•  .  -U . .  '•  •  V.-H#- 

...  •  •  •  '•  *  '•••>.  . . . . ■  .  .  »>.  »..  *?>» 

.  .  !.  »  .  "  '*•:••*  rN .  i , .  ,1:  ,«•  ,H  ><*»*•«»«  i 

....  >.  1  *  ‘  *«  •  »•  "  >'  . •••..■».  *••••«.»  ,4 ,t,  «>•-.-/•*.#,«. *4' • 

.  •,*•••*  .•»<*•  •  ••  •• 

•  ••■*•,'••  ......... 

1  <  •  •  4  *  •  7  #  r  i:«»  ».»»*«•'•  *,■!•* » • 

'  *  ■’  '  •  •  '*«♦«  •  >4>  »  "•**  ». 

. '  ’  ‘  '  *  *  '  ’  '-‘o  M.  U  MM  i  *h4. 

.  .  , .  ,  \  ,  '  .  I  *■• 1  14  •  *  *  ‘  .  .  •  I  ’  »’  •  ■  » •  I- ,  ■  .  I .  ,, ,  .  .  ^  ,t.  f «...  •  I' »**'•«•  1 

.  *  '**  •»”« . .  •«  .....  ....  .  *•  (1  ' *  »■' v 

'  ■  ,  ’  .  '  •  * ‘*  ‘  *• 1  >•••:  ■  .* »»>,  •  r  •  fill 'J'1’  *’ 

.  •  •  . . »  ’.s . . . r 

•  •  •  '  '  '  •  . . .  .  i  ...... 

•  ‘  •  ..  .  •  •  m  |’|  '•  •»  I  {••>».  y  . 

.  i  ’  *  ’*  *•  •  >  ,  •  •  .  .•  •  1  •  '  .  ..4  i  u>tr  »Uh  ,.y3  .u .  .  ;:i.  •  .m  ...  .  *.'*•  •  " 

'  •  ■  ■  .  »  •  •“  ■  •  •  •  .  •  1  . .  .  ,  i  ■  •  •  1  t'.'l.l-.  • i  t  .  1  -  \  '  I 

’  .  ■  1  ' '  1 .  .  1  .'I  i«ii  '  ■  |W.-*«  •  1  y  •)  ■  v « • '  •  •  ...M"  '•>  .»t «.Ut< »  • 

•  •  •••.•«  ••<»»  ‘.‘m  :.*>■  •••  -  ••  •  **«■'  •  MMit 

*•••»•  .»«*  -•  .  .  •»  .  >  '.•uir'iv.  , 

»  ».'•!•••.•  v  •  ..  >«•''«  •.»  »•*.  1  i,  .. 

•  .  . .  t  ».  r  • »  >  ‘ •  • «  *  "  *  b*4'«**'^*  i  "4 •  T:  •  '*’M  ..(j,  .  . i  : 

*  ■  '*•  l*  •  •  1  •  '  '  - .  .. 

*  .  •*•%*•*•  "  '  '  ' 

.....  .  ■  •  •-  )  w  ..  ..  ..  . 

..  i.  •.* •  * 4^4 •  ****  >•'*•'<  •.  •(  ...i„  i, ... ,  ...i-  v  > 

,  .  ...  •*».  '•  •  N*  ••  -i.M  •  ••'.«•.  •  • 

•  n  .  •  f*  ^  >  ••  ' 

.  .  «*  '  ’■  •  -  ,  •  ■  »  ’»  ^  ..  •  s!  • 

....  .  t  .  .  >  .  ,»  . . .  M  t  ,  . . « 


,  .  ,  .  "  :C  ‘  4 '  * 

•  •  •  •  .  .  . . 

■■■■’•  •  ■  ■  41  •.  v'i  1,1  .Jj:1'*  > 

’  •  •  •'  ■  ■  ...  ,  •  •  • 

.  i  ■  ....  •  •  ,  ••>.,  ,.  .  .  .  .■  •  •••  ‘  '♦•'i . 


’  •  •  •»  •  •  *  -1 

•  ■  ■.  ...  .  . 


I  l  {  .1 

•  ;  f  Mi  »  i»  1  "• 

•  H  •*.  i 

"  ■  -1  . . . 


■Jl 


Pi 


wkM. 


The  person  charging  this  material  is  re¬ 
sponsible  for  its  return  to  the  library  from 
which  it  was  withdrawn  on  or  before  the 
Latest  Date  stamped  below. 


Theft,  mutilation,  and  underlining  of  books  are  reasons 
for  disciplinary  action  and  may  result  in  dismissal  from 
the  University. 

To  renew  call  Telephone  Center,  333-8400 

UNIVERSITY  OF  ILLINOIS  LIBRARY  AT  URBANA-CHAMPAIGN 


ft  f  n 

i  J  O 


iVoi/  2.3  '0 


m  1?  h 


0;  l  i 


JLy 


jun  1 2  19b9 


mm 


MmM 


\*L. 

wUV,  T»,\cO  .• 


\  ■■ 


jb*. 


v I  •' •  4 


r;'v*  *• 

/  ‘S,vcT 


it':- 

-  "r  « 
*>»  v^r;  V 

& 

$sts 

^SSt-tk'y 

iMl  ■  ;v< 

jiyi 

p‘i 


■■■ . 


mmk 


LIBRARY 

OF  THE. 

UNIVERSITY  OF  ILLINOIS 


CHARLES  DARWIN 


THE 


ORIGIN  OF  SPECIES 

BY 

MEANS  OF  NATURAL  SELECTION; 

OR,  THE 


PRESERVATION  OF  FAVORED  RACES  IN  THE 

STRUGGLE  FOR  LIFE. 


By  CHARLES  DARWIN,  M.A.,  F.R.S., 

Author  of  “The  Descent  of  Man  ”  etc.,  etc. 


Reprinted  from  the  Sixth  London  Edition,  with  all  Additions  and 

Corrections. 


A.  L.  BURT  COMPANY,  PUBLISHERS, 
52-58  Duane  Street,  New  York. 


J 


/  0 


CXK-4&  t  /  & 


“  But  with  regard  to  the  material  world,  we  can  at  least 
go  so  far  as  this — we  can  perceive  that  events  are  brought 
about  not  by  insulated  interpositions  of  Divine  power, 
exerted  in  each  particular  case,  but  by  the  establishment 
of  general  laws.” — Whewell:  Bridgewater  Treatise . 

“The  only  distinct  meaning  of  the  word  *  natural*  is 
stated ,  fixed  or  settled;  since  what  is  natural  as  much  re¬ 
quires  and  presupposes  an  intelligent  agent  to  render  it  so, 
i.e.,  to  effect  it  continually  or  at  stated  times,  as  what  is 
supernatural  or  miraculous  does  to  effect  it  for  once.** — 
Butler:  Analogy  of  Revealed  Religio7i . 

“  To  conclude,  therefore,  let  no  man  out  of  a  weak  con- 
J  ceit  of  sobriety,  or  an  ill-applied  moderation,  think  or 
maintain,  that  a  man  can  search  too  far  or  be  too  well 
studied  in  the  book  of  God*s  word,  or  in  the  book  of  God*s 
o  works;  divinity  or  philosophy;  but  rather  let  men 
d  endeavor  an  endless  progress  or  proficience  in  both.** — 
Bacon:  Advancement  of  Learning. 


AN  HISTORICAL  SKETCH 


OP  THE  PROGRESS  OP  OPINION  ON  THE  ORIGIN 

OF  SPECIES, 

PREVIOUSLY  TO  THE  PUBLICATION  OF  THE  FIRST  EDITION 

OF  THIS  WORK. 


I  will  here  give  a  brief  sketch  of  the  progress  of  opin¬ 
ion  on  the  Origin  of  Species.  Until  recently  the  great 
majority  of  naturalists  believed  that  species  were  immut¬ 
able  productions,  and  had  been  separately  created.  This 
view  has  been  ably  maintained  by  many  authors.  Some 
few  naturalists,  on  the  other  hand,  have  believed  that 
species  undergo  modification,  and  that  the  existing  forma 
of  life  are  the  descendants  by  true  generation  of  pre  exist¬ 
ing  forms.  Passing  over  allusions  to  the  subject  in  the 
classical  writers,*  the  first  author  who  in  modern  times 

*Aristotle,  in  his  “Physicse  Auscultationes  ”  (lib.  2,  cap.  8,  s.  2), 
after  remarking  that  rain  does  not  fall  in  order  to  make  the  corn 
grow,  any  more  than  it  falls  to  spoil  the  farmer’s  corn  when  threshed 
out  of  doors,  applies  the  same  argument  to  organization;  and  adds  (as 
translated  by  Mr.  Clair  Grece,  who  first  pointed  out  the  passage  to 
me),  “  So  what  hinders  the  different  parts  [of  the  body]  from  having 
this,  merely  accidental  relation  in  nature  ?  as  the  teeth,  for  example, 
grow  by  necessity,  the  front  ones  sharp,  adapted  for  dividing,  and  the 
grinders  flat,  and  serviceable  for  masticating  the  food;  since  they 
were  not  made  for  the  sake  of  this,  but  it  was  the  result  of  accident. 
And  in  like  manner  as  to  other  parts  in  which  there  appears  to  exist 
an  adaptation  to  an  end.  Wheresoever,  therefore,  all  things 
together  (that  is  all  the  parts  of  one  whole)  happened  like  as  if  they 
were  made  for  the  sake  of  something,  these  were  preserved,  having 
been  appropriately  constituted  by  an  internal  spontaneity;  and  what¬ 
soever  things  were  not  thus  constituted,  perished  and  still  perish.’1 
We  here  see  the  principle  of  natural  selection  shadowed  forth,  but 
how  little  Aristotle  fully  comprehended  the  principle,  is  shown  by 
his  remarks  on  the  formation  of  the  teeth. 


vi 


HISTORICAL  SKETCH. 


has  treated  it  in  a  scientific  spirit  was  Buffon.  Bu-  as  his 
opinions  fluctuated  greatly  at  different  periods,  and  as  he 
does  not  enter  on  the  causes  or  means  of  the  transforma¬ 
tion  of  species,  I  need  not  here  enter  on  details. 

Lamarck  was  the  first  man  whose  conclusions  on  the 
subject  excited  much  attention.  This  justly  celebrated 
naturalist  first  published  his  views  in  1801;  he  much  en¬ 
larged  them  in  1809  in  his  “  Philosophic  Zoologique,”  and 
subsequently,  1815,  in  the  Introduction  to  his  “  Ilist.  Nat. 
des  Animaux  sans  Vertebres.”  In  these  works  he  upholds 
the  doctrine  that  all  species,  including  man,  are  descended 
from  other  species.  He  first  did  the  eminent  service  of 
arousing  attention  to  the  probability  of  all  change  in  the 
organic,  as  well  as  in  the  inorganic  world,  being  the  result 
of  law,  and  not  of  miraculous  interposition.  Lamarck 
seems  to  have  been  chiefly  led  to  his  conclusion  on  the 
gradual  change  of  species,  by  the  difficulty  of  distinguish¬ 
ing  species  and  varieties,  by  the  almost  perfect  gradation 
of  forms  in  certain  groups,  and  by  the  analogy  of  domestic 
productions.  With  respect  to  the  means  of  modification, 
he  attributed  something  to  the  direct  action  of  the  phys¬ 
ical  conditions  of  life,  something  to  the  crossing  of 
already  existing  forms,  and  much  to  use  and  disuse,  that 
is,  to  the  effects  of  habit.  To  this  latter  agency  he  seems 
to  attribute  all  the  beautiful  adaptations  in  nature;  such, 
as  the  long  neck  of  the  giraffe  for  browsing  on  the  branches 
of  trees.  But  he  likewise  believed  in  a  law  of  progressive 
development;  and  as  all  the  forms  of  life  thus  tend  to 
progress,  in  order  to  account  for  the  existence  at  the 
present  day  of  simple  productions,  he  maintains  that  such 
forms  are  now  spontaneously  generated.* 

Geoffroy  Saint-Hilaire,  as  is  stated  in  his  “Life,”  writ¬ 
ten  by  his  son,  suspected,  as  early  as  1795,  that  what  we 
call  species  are  various  degenerations  of  the  same  type.  It 

*  I  have  taken  the  date  of  the  first  publication  of  Lamarck  from 
Isidore  Geoffroy  Saint-Hilaire’s  (“ftist.  Nat.  Generale, ”  tom.  ii.  pt 
405,  1859)  excellent  history  of  opinion  on  this  subject.  In  this  work 
a  full  account  is  given  of  Buff  on’s  conclusions  on  the  same  subject. 
It  is  curious  how  largely  my  grandfather.  Dr.  Erasmus  Darwin, 
anticipated  the  views  and  erroneous  grounds  of  opinion  of  Lamarck 
in  his  “  Zoonomia”  (vol.  i.  pp.  500-510),  published  in  1794.  Accord¬ 
ing  to  Isid.  Geoffroy  there  is  no  doubt  that  Goethe  was  an  extreme 
partisan  of  similar  views,  as  shown  in  the  introduction  to  a  work 


HISTORICAL  SKETCH. 


Vll 

was  not  until  1828  that  he  published  his  conviction  that 
the  same  forms  have  not  been  perpetuated  since  the  origin 
of  all  things.  Geoffroy  seems  to  have  relied  chiefly  on  the 
conditions  of  life,  or  the  “  monde  ambiant”  as  the  cause  of 
change.  He  was  cautious  in  drawing  conclusions,  and  did 
not  believe  that  existing  species  are  now  undergoing  modi¬ 
fication;  and,  as  his  son  adds,  “C*est  done  un  probleme  a 
reserver  enticement  4  Favenir,  suppose  meme  que  Favenir 
doive  avoir  prise  sur  lui.” 

In  1813  Dr.  W.  0.  Wells  read  before  the  Royal  Society 
“  An  Account  of  a  White  Female,  part  of  whose  skin 
resembles  that  of  a  Negro  ;  ”  but  his  paper  was  not  pub¬ 
lished  until  his  famous  “  Two  Essays  upon  Dew  and  Single 
Vision  ”  appeared  in  1818.  In  this  paper  he  distinctly 
recognizes  the  principle  of  natural  selection,  and  this  is  the 
first  recognition  which  has  been  indicated;  but  he  applies 
it  only  to  the  races  of  man,  and  to  certain  characters  alone. 
After  remarking  that  negroes  and  mulattoes  enjoy  an  im¬ 
munity  from  certain  tropical  diseases,  he  observes,  firstly, 
that  all  animals  tend  to  vary  in  some  degree,  and,  secondly, 
that  agriculturists  improve  their  domesticated  amiinals  by 
selection;  and  then,  he  adds,  but  what  is  done  in  this 
latter  case  “  by  art,  seems  to  be  done  with  equal  efficacy, 
though  more  slowly,  by  nature,  in  the  formation  of  varie¬ 
ties  of  mankind,  fitted  for  the  country  which  they  inhabit. 
Of  the  accidental  varieties  of  man,  which  would  occur 
among  the  first  few  and  scattered  inhabitants  of  the  middle 
regions  of  Africa,  some  one  would  be  better  fitted  than 
others  to  bear  the  diseases  of  the  country.  This  race 
would  consequently  multiply,  while  the  others  would 
decrease;  not  only  from  their  inability  to  sustain  the 
attacks  of  disease,  but  from  their  incapacity  of  contending 
with  their  more  vigorous  neighbors.  The  color  of  this 
vigorous  race  I  take  for  granted,  from  what  has  been 

written  in  1794  and  1795,  but  not  published  till  long  afterward  be 
bas  pointedly  remarked  (“Goethe  als  Naturforscher,”  von  Dr.  Karl 
Meding,  s.  34)  that  the  future  question  for  naturalists  will  be  bow,  for 
instance,  cattle  got  their  horns  and  not  for  what  they  are  used.  It  is 
rather  a  singular  instance  of  the  manner  in  which  similar  views  arise 
at  about  the  same  time,  that  Goethe  in  Germany,  Dr,  Darwin  in  Eng¬ 
land,  and  Geoffroy  Saint- Hilaire  (as  we  shall  immediately  see)  in 
France,  came  to  the  same  conclusion  on  the  origin  of  suedes,  in  the 
years  1794-5- 


HISTORICAL  SKETCH. 


•  •  9 

Vlll 

already  said,  would  be  dark.  But  the  same  disposition  to 
form  varieties  still  existing,  a  darker  and  a  darker  race 
would  in  the  course  of  time  occur:  and  as  the  darkest 
would  be  the  best  fitted  for  the  climate,  this  would  at 
length  become  the  most  prevalent,  if  not  the  only  race,  in 
the  particular  country  in  which  it  had  originated."  He 
then  extends  these  same  views  to  the  white  inhabitants  of 
colder  climates.  I  am  indebted  to  Mr.  Rowley,  of  the 
United  States,  for  having  called  my  attention,  through  Mr. 
Brace,  to  the  above  passage  of  Hr.  Wells*  work. 

The  Hon.  and  Rev.  W.  Herbert,  afterward  Dean  of 
Manchester,  in  the  fourth  volume  of  the  “  Horticultural 
Transactions,"  1822,  and  in  his  work  on  the  “  Amarylli- 
daceaa"  (1837,  pp.  19,  339),  declares  that  “horticultural 
experiments  have  established,  beyond  the  possibility  of 
refutation,  that  botanical  species  are  only  a  higher  and 
more  permanent  class  of  varieties."  He  extends  the  same 
view  to  animals.  The  dean  believes  that  single  species  of 
each  genus  were  created  in  an  originally  highly  plastic  con¬ 
dition,  and  that  these  have  produced,  chiefly  by  inter¬ 
crossing,  but  likewise  by  variation,  all  our  existing  species. 

In  1826  Professor  Grant,  in  the  concluding  paragraph 
in  his  well-known  paper  (“Edinburgh  Philosophical 
Journal,"  vol.  xiv,  p.  283)  on  the  Spongilla,  clearly  de¬ 
clares  his  belief  that  species  are  descended  from  other 
species,  and  that  they  become  improved  in  the  course  of 
modification.  This  same  view  was  given  in  his  Fifty-fifth 
Lecture,  published  in  the  “  Lancet"  in  1834. 

In  1831  Mr.  Patrick  Matthew  published  his  work  on 
“  Naval  Timber  and  Arboriculture,"  in  which  he  gives 
precisely  the  same  view  on  the  origin  of  species  as  that 
(presently  to  be  alluded  to)  propounded  by  Mr.  Wallace 
and  myself  in  the  “Linnean  Journal,"  and  as  that  enlarged 
in  the  present  volume.  Unfortunately  the  view  was  given 
by  Mr.  Matthew  very  briefly  in  scattered  passages  in  an 
appendix  to  a  work  on  a  different  subject,  so  that  it  re¬ 
mained  unnoticed  until  Mr.  Matthew  himself  drew  atten¬ 
tion  to  it  in  the  “  Gardeners*  Chronicle,"  on  April  7, 
1860.  The  differences  of  Mr.  Matthew’s  views  from  mine 
are  not  of  much  importance:  he  seems  to  consider  that  the 
world  was  nearly  depopulated  at  successive  periods,  and 
then  restocked;  and  lie  gives  as  an  alternative,  that  new 


HISTORICAL  SKETCH. 


in¬ 
forms  may  be  generated  “  without  the  presence  of  any 
mold  or  germ  of  former  aggregates.”  I  am  not  sure  that 
I  understand  some  passages;  but  it  seems  that  he  attributes 
much  influence  to  the  direct  action  of  the  conditions  of 
life.  He  clearly  saw,  however,  the  full  force  of  the  prin¬ 
ciple  of  natural  selection. 

The  celebrated  geologist  and  naturalist.  Yon  Buch,  in 
his  excellent  “  Description  Physique  des  Isles  Canaries” 
(1836,  p.  147),  clearly  expresses  his  belief  that  varieties 
slowly  become  changed  into  permanent  species,  which  are 
no  longer  capable  of  intercrossing. 

Rafinesque,  in  his  “New  Flora  of  North  America,”  pub¬ 
lished  in  1836,  wrote  (p.  6)  as  follows:  “All  species  might 
have  been  varieties  once,  and  many  varieties  are  gradually 
becoming  species  by  assuming  constant  and  peculiar  char¬ 
acters;”  but  further  on  (p.  18)  he  adds,  “except  the 
original  types  or  ancestors  of  the  genus.” 

In  1843-44  Professor  Haldeman  (“  Boston  Journal  of 
Nat.  Hist.  U.  States,”  vol.  iv,  p.  468)  has  ably  given  the 
arguments  for  and  against  the  hypothesis  of  the  develop¬ 
ment  and  modification  of  species:  he  seems  to  lean  toward 
the  side  of  change. 

The  “Vestiges  of  Creation”  appeared  in  1844.  In  the 
tenth  and  much  improved  edition  (1853)  the  anony¬ 
mous  author  says  (p.  155):  “The  proposition  determined 
on  after  much  consideration  is,  that  the  several  series 
of  animated  beings,  from  the  simplest  and  oldest  up  to 
the  highest  and  most  recent,  are,  under  the  providence 
of  God,  the  results,  first,  of  an  impulse  which  has  been  im¬ 
parted  to  the  forms  of  life,  advancing  them,  in  definite 
times,  by  generation,  through  grades  of  organization  ter¬ 
minating  in  the  highest  dicotyledons  and  vertebrata,  these 
grades  being  few  in  number,  and  generally  marked  by  in- 
tervals  of  organic  character,  which  we  find  to  be  a  practi 
cal  difficulty  in  ascertaining  affinities;  second ,  of  another 
impulse  connected  with  the  vital  forces,  tending,  in  the 
course  of  generations,  to  modify  organic  structures  in  ac¬ 
cordance  with  external  circumstances,  as  food,  the  nature 
of  the  habitat,  and  the  meteoric  agencies,  these  being  the 
‘  adaptations 9  of  the  natural  theologian.”  The  author  ap¬ 
parently  believes  that  organization  progresses  by  sudden 
leaps,  but  that  the  effects  produced  by  the  conditions  of 


X 


HISTORICAL  SKETCH. 


life  are  gradual.  He  argues  with  much  force  on  general 
grounds  that  species  are  not  immutable  productions.  But 
I  cannot  see  how  the  two  supposed  “impulses”  account  in  a 
scientific  sense  for  the  numerous  and  beautiful  coadaptations 
which  we  see  throughout  nature;  1  cannot  see  that  we 
thus  gain  any  insight  how,  for  instance,  a  woodpecker  has 
become  adapted  to  its  peculiar  habits  of  life.  The  work, 
from  its  powerful  and  brilliant  style,  though  displaying  in 
the  early  editions  little  accurate  knowledge  and  a  great 
want  of  scientific  caution,  immediately  had  a  very  wide 
circulation.  In  my  opinion  it  has  done  excellent  service 
in  this  country  in  calling  attention  to  the  subject,  in  re¬ 
moving  prejudice,  and  in  thus  preparing  the  ground  for 
the  reception  of  analogous  views. 

In  1846  the  'Veteran  geologist  M.  J.  d’Omalius  d*Halloy 
published  in  an  excellent  though  short  paper  (“  Bulletins 
de  PAcad.  Boy.  Bruxelles,”  tom.  xiii,  p.  581)  his  opinion 
that  it  is  more  probable  that  new  species  have  been  pro¬ 
duced  by  descent  with  modification  than  that  they  have 
been  separately  created:  the  author  first  promulgated  this 
opinion  in  1831. 

Professor  Owen,  in  18 19  (“Nature  of  Limbs,”  p.  86), 
wrote  as  follows:  “  The  archetypal  idea  was  manifested 
in  the  flesh  under  diverse  such  modifications,  upon  this 
planet,  long  prior  to  the  existence  of  those  animal  species 
that  actually  exemplify  it.  To  what  natural  laws  or  secon¬ 
dary  causes  the  orderly  succession  and  progression  of  such 
organic  phenomena  may  have  been  committed,  we,  as  yet, 
are  ignorant.”  In  his  address  to  the  British  Association, 
in  1858,  he  speaks  (p.  li)  of  “the  axiom  of  the  continuous 
operation  of  creative  power,  or  of  the  ordained  becoming 
of  living  things.”  Further  on  (p.  xc),  after  referring  to 
geographical  distribution,  he  adds,  “These  phenomena 
shake  our  confidence  in  the  conclusion  that  the  Apteryx  of 
New  Zealand  and  the  Red  Grouse  of  England  were  distinct 
creations  in  and  for  those  islands  respectively.  Always, 
also,  it  may  be  well  to  bear  in  mind  that  by  the  word 
‘creation*  the  ’zoologist  means  ‘a  process  he  knows  not 
what.*”  He  amplifies  this  idea  by  adding  that  when  such 
cases  as  that  of  the  Red  Grouse  are  “enumerated  by  the 
zoologist  as  evidence  of  distinct  creation  of  the  bird  in  and 
for  such  islands,  he  chiefly  expresses  that  he  knows  not 


HISTORICAL  SKETCH \ 


XL 

how  the  Red  Grouse  came  to  be  there,  and  there  exclu¬ 
sively;  signifying  also,  by  this  mode  of  expressing  such 
ignorance,  his  belief  that  both  the  bird  and  the  islands 
owed  their  origin  to  a  great  first  Creative  Cause.”  If  we 
interpret  these  sentences  given  in  the  same  address,  one  by 
the  other,  it  appears  that  this  eminent  philosopher  felt  in 
1858  his  confidence  shaken  that  the  Apteryx  and  the  Red 
Grouse  first  appeared  in  their  respective  homes  “  he  knew 
not  how,”  or  by  some  process  “  he  knew  not  what.” 

This  address  was  delivered  after  the  papers  by  Mr. 
Wallace  and  myself  on  the  Origin  of  Species,  presently  to 
be  referred  to,  had  been  read  before  the  Linnean  Society 
When  the  first  edition  of  this  work  was  published,  I  was 
so  completely  deceived,  as  were  many  others,  by  such 
expressions  as  “  the  continuous  operation  of  creative 
power,”  that  I  included  Professor  Owen  with  other  palaeon¬ 
tologists  as  being  firmly  convinced  of  the  immutability  of 
species;  but  it  appears  (“Anat.  of  Vertebrates,”  vol.  iii, 
p.  796)  that  this  was  on  my  part  a  preposterous  error.  In 
the  last  edition  of  this  work  I  inferred,  and  the  inference 
still  seems  to  me  perfectly  just,  from  a  passage  beginning 
with  the  words  “  no  doubt  the  type-form,”  etc.  (Ibid.,  vol. 
i,  p.  xxxv),  that  Professor  Owen  admitted  that  natural 
selection  may  have  done  something  in  the  formation  of  a 
new  species  ;  but  this  it  appears  (Ibid.,  vol.  iii,  p.  798)  is 
inaccurate  and  without  evidence.  I  also  gave  some  extracts 
from  a  correspondence  between  Professor  Owen  and  the 
editor  of  the  “  London  Review,”  from  which  it  appeared 
manifest  to  the  editor  as  well  as  to  myself,  that  Professor 
Owen  claimed  to  have  promulgated  the  theory  of  natural 
selection  before  I  had  done  so ;  and  I  expressed  my  sur¬ 
prise  and  satisfaction  at  this  announcement ;  but  as  far  as 
it  is  possible  to  understand  certain  recently  published  pas¬ 
sages  (Ibid.,  vol.  iii,  p.  798)  I  have  either  partially  or 
wholly  again  fallen  into  error.  It  is  consolatory  to  me 
that  others  find  Professor  Owen’s  controversial  writings  as 
difficult  to  understand  and  to  reconcile  with  each  other,  as 
I  do.  As  far  as  the  mere  enunciation  of  the  principle  of 
natural  selection  is  concerned,  it  is  quite  immaterial 
whether  or  not  Professor  Owen  preceded  me,  for  both  of 
us,  as  shown  in  this  historical  sketch,  were  long  ago  pre¬ 
ceded  by  Dr.  Wells  and  Mr.  Matthews.  > 


HISTORICAL  SKETCH. 


•  • 

Xll 

M.  Isidore  Geoffroy  Saint-Hilaire,  in  his  lectures  deliv¬ 
ered  in  1850  (of  which  a  Resume  appeared  in  the  “  Revue 
et  Mag.  de  Zoolog.,"  Jan.,  1851),  briefly  gives  his  reason 
for  believing  that  specific  characters  “sont  fixes,  pour 
chaque  espece,  tant  qu’elle  se  perpetue  au  milieu  des 
mbmes  circonstances:  ils  se  modifient,  si  les  circonstances 
ambiantes  viennent  a  changer."  “En  resume,  V observa¬ 
tion  des  animaux  sauvages  demontre  deja  la  variability 
limit  ee  des  especes.  Les  experiences  sur  les  animaux 
sauvages  devenus  domestiques,  et  sur  les  animaux  domes- 
tiques  redevenus  sauvages,  la  demontrent  plus  clairement 
encore.  Ces  memes  experiences  prouvent,  de  plus,  que  les 
differences  produites  peuvent  etre  de  valeur  generique.” 
In  his  “  Hist.  Nat.  Generate"  (tom.  ii,  p.  430,  1859)  he 
amplifies  analogous  conclusions. 

From  a  circular  lately  issued  it  appears  that  Dr.  Freke, 
in  1851  (“  Dublin  Medical  Press,"  p.  322),  propounded 
the  doctrine  that  all  organic  beings  have  descended  from 
one  primordial  form.  His  grounds  of  belief  and  treat¬ 
ment  of  the  subject  are  wholly  different  from  mine ; 
but  as  Dr.  Freke  has  now  (1861)  published  his  Essay  on 
ihe  “  Origin  of  Species  by  means  of  Organic  Affinity," 
the  difficult  attempt  to  give  any  idea  of  his  views  would 
be  superfluous  on  my  part. 

Mr.  Herbert  Spencer,  in  an  Essay  (originally  pub¬ 
lished  in  the  “  Leader,"  March,  1852,  and  republished  in 
his  “Essays,"  in  1858),  has  contrasted  the  theories  of  the 
Creation  and  the  Development  of  organic  beings  with 
remarkable  skill  and  force.  He  argues  from  the  analogy 
of  domestic  productions,  from  the  changes  which  the  em¬ 
bryos  of  many  species  undergo,  from  the  difficulty  of  dis¬ 
tinguishing  species  and  varieties,  and  from  the  principle  of 
general  gradation,  that  species  have  been  modified;  and 
he  attributes  the  modification  to  the  change  of  circum¬ 
stances.  The  author  (1855)  has  also  treated  Psychology 
on  the  principle  of  the  necessary  acquirement  of  each 
mental  power  and  capacity  by  gradation. 

In  1852  M.  Naudin,  a  distinguished  botanist,  expressly 
stated,  in  an  admirable  paper  on  the  Origin  of  Species 
(“Revue  Horticole,"  p.  10^;  since  partly  republished  in 
the  “Nouvelles  Archives  du  Museum,"  tom.  i,  p.  171),  his 
belief  that  species  are  formed  in  an  analogous  manner  as 


historical,  sketch. 


•  9  C 

Xlll 

varieties  are  under  cultivation  ;  and  tlie  latter  process  he 
attributes  to  man’s  power  of  selection.  But  he  does  not 
show  how  selection  acts  under  nature.  He  believes, 
like  Dean  Herbert,  that  species,  when  nascent,  were  more 
plastic  than  at  present.  He  lays  weight  on  what  he  calls 
the  principle  of  finality,  “  puissance  mysterieuse,  inde- 
termin6e ;  fatalite  pour  les  uns ;  pour  les  autres  volonte 
providentielle,  dont  l’action  incessante  sur  les  6tres  vi- 
vantes  determine,  a  toutes  les  epoques  de  l’existence  du 
monde,  la  forme,  le  volume,  et  la  duree  de  cliacun  d’eux, 
en  raison  de  sa  destinee  dans  l’ordre  de  choses  dont  il  fait 
partie.  C’est  cette  puissance  qui  harmonise  chaque 
membre  a  Pensemble,  en  Pappropriant  a  la  fonction  qu’il 
doit  remplir  dans  Porganisme  general  de  la  nature,  fonc¬ 
tion  qui  est  pour  lui  sa  raison  d’etre.”  * 

In  1853  a  celebrated  geologist,  Count  Keyserling  (“Bul¬ 
letin  de  la  Soc.  Geolog.,”  2d  Ser.,  tom.  x,  p.  357),  sug¬ 
gested  that  as  new  diseases,  supposed  to  have  been  caused 
by  some  miasma  have  arisen  and  spread  over  the  world,  so 
at  certain  periods  the  germs  of  existing  species  may  have 
been  chemically  affected  by  circumambient  molecules  of  a 
particular  nature,  and  thus  have  given  rise  to  new  forms. 

In  this  same  year,  1853,  Dr.  Schaaffhausen  published  an 
excellent  pamphlet  (“Verhand.  des  Naturhist.  Vereins  der 
Preuss.  Rheinlands,”  etc.),  in  which  he  maintains  the  de¬ 
velopment  of  organic  forms  on  the  earth.  He  infers  that 
many  species  have  kept  true  for  long  periods,  whereas  a 
few  have  become  modified.  The  distinction  of  species  he 
explains  by  the  destruction  of  intermediate  graduated 


*From  references  in  Bronn’s  "  Untersuchungen  iiber  dieEnt- 
wickelungs-Gesetze,”  it  appears  that  the  celebrated  botanist  and 
palaeontologist  Unger  published,  in  1852,  his  belief  that  species 
undergo  development  and  modification.  Dalton,  likewise,  in  Pander 
and  Dalton’s  work  on  Fossil  Sloths,  expressed,  in  1821,  a  similar 
belief.  Similar  views  have,  as  is  well  known,  been  maintained  by 
Oken  in  his  mystical  “  Natur-Philosopliie.”  From  other  references 
in  Godron’s  work  “Sur  l’Espece,”  it  seems  that  Bory  St.  Vincent, 
Burdach,  Poiret  and  Fries,  have  all  admitted  that  new  species  are 
continually  being  produced.  I  may  add,  that  of  the  thirty-four 
authors  named  in  this  Historical  Sketch,  who  believe  in  the  modi- 
cation  of  species,  or  at  least  disbelieve  in  separate  acts  of  crea¬ 
tion,  twenty-seven  have  written  on  special  branches  of  natural 
history  or  geology. 


xiv 


HISTORICAL  SKETCH. 


forms.  <e  Thus  living  plants  and  animals  are  not  sepa¬ 
rated  from  the  extinct  by  new  creations,  but  are  to  b© 
regarded  as  their  descendants  through  continued  repro¬ 
duction.” 

A  well-known  French  botanist,  M.  Lecoq,  writes  in 
1854  (“Etudes  sur  Geograph.  Bot.  tom.  i,  p.  250),  “On 
voit  que  nos  recherches  sur  la  fixite  ou  la  variation  de 
Tespece,  nous  conduisent  directement  aux  idees  emises 
par  deux  hommes  justement  celebres,  Geoffroy  Saint- 
Hilaire  et  Goethe.”  Some  other  passages  scattered  through 
M.  Lecoq’s  large  work  make  it  a  little  doubtful  how  far  lie 
extends  his  views  on  the  modification  of  species. 

The  “  Philosophy  of  Creation  ”  has  been  treated  in  a 
masterly  manner  by  the  Rev.  Baden  Powell,  in  his  “  Essays 
on  the  Unity  of  Worlds,”  1855.  Nothing  can  be  more 
striking  than  the  manner  in  which  he  shows  that  the  intro¬ 
duction  of  new  species  is  “a  regular,  not  a  casual  phenom¬ 
enon,”  or,  as  Sir  John  Herschel  expresses  it,  “  a  natural 
in  contradistinction  to  a  miraculous  process.” 

The  third  volume  of  the  “Journal  of  the  Linnean 
Society”  contains  papers,  read  July  1,  1858,  by  Mr. 
Wallace  and  myself,  in  which,  as  stated  in  the  introductory 
remarks  to  this  volume,  the  theory  of  Natural  Selection  is 
promulgated  by  Mr.  Wallace  with  admirable  force  and 
clearness. 

Yon  Baer,  toward  whom  all  zoologists  feel  so  profound  a 
respect,  expressed  about  the  year  1859  (see  Prof.  Rudolph 
Wagner,  “  Zoologisch-Anthropologische  Untersuchungen,” 
1861,  s.  51)  his  conviction,  chiefly  grounded  on  the  laws  of 
geographical  distribution,  that  forms  now  perfectly  distinct 
have  descended  from  a  single  parent-form. 

In  June,  1859,  Professor  Huxley  gave  a  lecture  before 
the  Royal  Institution  on  the  “  Persistent  Types  of  Animal 
Life.”  Referring  to  such  cases,  he  remarks,  “  It  is  difficult 
to  comprehend  the  meaning  of  such  facts  as  these,  if  we 
suppose  that  each  sjoecies  of  animal  and  plant,  or  each 
great  type  of  organization,  was  formed  and  placed  upon  the 
surface  of  the  globe  at  long  intervals  by  a  distinct  act  of 
creative  power;  and  it  is  'well  to  recollect  that  such  an 
assumption  is  as  unsupported  by  tradition  or  revelation  as 
it  is  opposed  to  the  general  analogy  of  nature.  If,  on  the 
other  hand,  we  view  “ Persistent  Types”  in  relation  to 


HISTORICAL  SKETCH. 


XV 

that  hypothesis  which  supposes  the  species  living  at  any 
time  to  be  the  result  of  the  gradual  modification  of  pre¬ 
existing  species,  a  hypothesis  which,  though  unproven,  and 
'  sadly  damaged  by  some  of  its  supporters,  is  yet  the  only 
one  to  which  physiology  lends  any  countenance;  their 
existence  would  seem  to  show  that  the  amount  of  modifica¬ 
tion  which  living  beings  have  undergone  during  geological 
time  is  but  very  small  in  relation  to  the  whole  series  of 
changes  which  they  have  suffered.” 

In  December,  1859,  Dr.  Hooker  published  his  “  Intro¬ 
duction  to  the  Australian  Flora.”  In  the  first  part  of  this 
great  Work  he  admits  the  truth  of  the  descent  and  modifica¬ 
tion  of  species,  and  supports  this  doctrine  by  many  original 
observations. 

The  first  edition  of  this  work  was  published  on  Novem¬ 
ber  24,  1859,  and  the  second  edition  on  January  7,  1860. 


CONTENTS. 


Introduction 


PiGS. 
..  1 


CHAPTER  I. 

VARIATION  UNDER  DOMESTICATION. 

Causes  of  Variability — Effects  of  Habit  and  tbe  use  or  disuse 
of  Parts — Correlated  Variation — Inheritance — Character  of 
Domestic  Varieties — Difficulty  of  distinguishing  between 
Varieties  and  Species — Origin  of  Domestic  Varieties  from 
one  or  more  Species — Domestic  Pigeons,  their  Differences 
and  Origin — Principles  of  Selection,  anciently  followed, 
their  Effects  —  Methodical  and  Unconscious  Selection — 
Unknown  Origin  of  our  Domestic  Productions— Circum¬ 
stances  favorable  to  Man’s  power  of  Selection .  6 

CHAPTER  II. 

VARIATION  UNDER  NATURE. 

Variability  —  Individual  differences — Doubtful  species  —  Wide 
ranging,  much  diffused,  and  common  species,  vary  most — 
Species  of  the  larger  genera  in  each  country  vary  more 
frequently  than  the  species  of  the  smaller  genera — Many 
of  the  species  of  the  larger  genera  resemble  varieties  in 
being  very  closely,  but  unequally,  related  to  each  other,  and 
in  having  restricted  ranges . 39 

CHAPTER  III. 

STRUGGLE  FOR  EXISTENCE. 

Its  bearing  on  natural  selection  —  The  term  used  in  a  wide 
sense  —  Geometrical  ratio  of  increase  —  Rapid  increase  of 
naturalized  animals  and  plants — Nature  of  the  checks  to 
increase — Competition  universal — Effects  of  climate — Pro¬ 
tection  from  the  number  of  individuals — Complex  relations 
of  all  animals  and  plants  throughout  nature — Struggle  for 


CONTENTS. 


XVlll 

life  most  severe  between  individuals  and  varieties  of  the 
same  species:  often  severe  between  species  of  the  same 
genus — The  relation  of  organism  to  organism  the  most 
important  of  all  relations . 57 

CHAPTER  IV. 

NATURAL  SELECTION;  OR  THE  SURVIVAL  OF  THE  FITTEST. 

Natural  Selection — its  power  compared  with  man’s  selection— 
its  power  on  characters  of  trifling  importance — its  power 
at  all  ages  and  on  both  sexes — Sexual  Selection — On  the 
generality  of  intercrosses  between  individuals  of  the  same 
species — Circumstances  favorable  and  unfavorable  to  the 
results  of  Natural  Selection,  namely,  intercrossing,  isolation, 
number  of  individuals — Slow  action — Extinction  caused  by 
Natural  Selection — Divergence  of  Character,  related  to  the 
diversity  of  inhabitants  of  any  small  area  and  to  naturaliza¬ 
tion — Action  of  Natural  Selection,  through  Divergence  of 
Character  and  Extinction,  on  the  descendants  from  a 
common  parent  —  Explains  the  grouping  of  all  organic 
beings — Advance  in  organization — Low  forms  preserved— 
Convergence  of  character  —  Indefinite  multiplication  of 
species — Summary . ..  73 


CHAPTER  V. 

LAWS  OF  VARIATION. 

Effects  of  changed  conditions  —  Use  and  disuse,  combined 
with  natural  selection;  organs  of  flight  and  of  vision — 
Acclimatization  —  Correlated  variation — Compensation  and 
economy  of  growth  —  False  correlations  —  Multiple,  rudi¬ 
mentary  and  lowly  organized  structures  variable  —  Parts 
developed  in  an  unusual  manner  are  highly  variable; 
specific  characters  more  variable  than  generic;  secondary 
sexual  characters  variable — Species  of  the  same  genus  vary 
in  an  analogous  manner — Reversions  to  long-lost  charac¬ 
ters — Summary . 126 


CHAPTER  VI. 

DIFFICULTIES  OF  THE  THEORY. 

Difficulties  of  the  theory  of  descent  with  modification— 
Absence  or  rarity  of  transitional  varieties — Transitions  in 
habits  of  life — Diversified  habits  in  the  same  species — ■ 
Species  with  habits  widely  different  from  those  of  their 
allies — Organs  of  extreme  perfection — Modes  of  transition — 
Cases  of  difficulty  —  Natura  non  facit  sal  turn — Organs  of 


CONTENTS. 


xix 

Page. 

small  importance — Organs  not  in  all  cases  absolutely  per¬ 
fect — The  law  of  Unity  of  Type  and  of  the  Conditions  of 
Existence  embraced  by  the  theory  of  Natural  Selection . 158 

CHAPTER  VII. 

MISCELLANEOUS  OBJECTIONS  TO  THE  THEORY  OF  NATURAL 

SELECTION. 

Longevity  —  Modifications  not  necessarily  simultaneous — Modi¬ 
fications  apparently  of  no  direct  service  —  Progressive 
development — Characters  of  small  functional  importance, 
the  most  constant — Supposed  incompetence  of  natural  selec 
tion  to  account  for  the  incipient  stages  of  useful  structures 
— Causes  which  interfere  with  the  acquisition  through 
natural  selection  of  useful  structures — Gradations  of  struct¬ 
ure  with  changed  functions  —  Widely  different  organs  in 
members  of  the  same  class,  developed  from  one  and  the 
same  source — Reasons  for  disbelieving  in  great  and  abrupt 
modifications . 199 


CHAPTER  VIII. 

INSTINCT. 

Jnstincts  comparable  with  habits,  but  different  in  their 
origin — Instincts  graduated  —  Aphides  and  ants  —  Instincts 
variable — Domestic  instincts,  their  origin — Natural,  instincts 
of  the  cuckoo,  molothrus,  ostrich  and  parasitic  bees — Slave¬ 
making  ants — Hive-bee,  its  cell-making  instinct — Changes 
of  instinct  and  structure  not  necessarily  simultaneous — 
Difficulties  of  the  theory  of  the  Natural  Selection  of  instincts 
— Neuter  or  sterile  insects — Summary . . . 242 

CHAPTER  IX. 

HYBRIDISM. 

Distinction  between  the  sterility  of  first  crosses  and  of 
hybrids — Sterility  various  in  degree,  not  universal,  affected 
by  close  interbreeding,  removed  by  domestication — Laws 
governing  the  sterility  of  hybrids — Sterility  not  a  special 
endowment,  but  incidental  on  other  differences,  not  accumu¬ 
lated  by  natural  selection — Causes  of  the  sterility  of  first 
crosses  and  of  hybrids — Parallelism  between  the  effects  of 
changed  conditions  of  life  and  of  crossing — Dimorphism  and 
Trimorphism  —  Fertility  of  varieties  when  crossed  and  of 
their  mongrel  offspring  not  universal — Hybrids  and  mon¬ 
grels  compared  independently  of  their  fertility — Summary... 277 


XX 


CONTENTS. 


CHAPTER  X. 

ON  THE  IMPERFECTION  OF  THE  GEOLOGICAL  RECORD. 

PAGB. 

On  tlie  absence  of  intermediate  varieties  at  tbe  present  day — 

On  tbe  nature  of  extinct  intermediate  varieties;  on  their 
number — On  tbe  lapse  of  time,  as  inferred  from  tbe  rate  of 
denudation  and  of  deposition — On  tbe  lapse  of  time  as  esti¬ 
mated  by  years — On  tbe  poorness  of  our  palaeontological  col¬ 
lections — On  tbe  intermittence  of  geological  formations — On 
tbe  denudation  of  granitic  areas — On  tbe  absence  of  inter¬ 
mediate  varieties  in  any  one  formation — On  tbe  sudden 
appearance  of  groups  of  species — On  tbeir  sudden  appear¬ 
ance  in  tbe  lowest  known  fossiliferous  strata — Antiquity  of 
tbe  habitable  eartb . 312 


CHAPTER  XI. 

ON  THE  GEOLOGICAL  SUCCESSION  OF  ORGANIC  BEINGS. 

On  tbe  slow  and  successive  appearance  of  new  species — On 
tbeir  different  rates  of  change  —  Species  once  lost  do  not 
reappear — Groups  of  species  follow  tbe  same  general  rules 
in  tbeir  appearance  and  disappearance  as  do  single  species 
— On  extinction — On  simultaneous  changes  in  tbe  forms 
of  life  throughout  tbe  world — On  tbe  affinities  of  extinct 
species  to  each  other  and  to  living  species — On  tbe  state  of 
development  of  ancient  forms — On  tbe  succession  of  tbe 
same  types  within  tbe  same  areas — Summary  of  preceding 
and  present  chapter . 343 


CHAPTER  XII. 

GEOGRAPHICAL  DISTRIBUTION. 

Present  distribution  cannot  be  accounted  for  by  differences 
in  physical  conditions  —  Importance  of  barriers  —  Affinity 
of  tbe  productions  of  the  same  continent — Centers  of  crea¬ 
tion — Means  of  dispersal  by  changes  of  climate  and  of  tbe 
level  of  tbe  land,  and  by  occasional  means — Dispersal  during 
tbe  Glacial  period — Alternate  Glacial  periods  in  tbe  north 
and  south . . . 373 


CHAPTER  XIII. 

geographical  distribution — continued. 

Distribution  of  fresh-water  productions  —  On  tbe  inhabitants 
of  oceanic  islands — Absence  of  Batracbians  and  of  terrestrial 
Mammals — On  tbe  relation  of  tbe  inhabitants  of  islands  to 


CONTENTS. 


xxi 

Page. 

those  of  the  nearest  mainland — On  colonization  from  the 
nearest  source  with  subsequent  modification — Summary  of 
the  last  and  present  chapter . 405 

CHAPTER  XIV. 

MUTUAL  AFFINITIES  OF  ORGANIC  BEINGS:  MORPHOLOGY — EMBRY¬ 
OLOGY — RUDIMENTARY  ORGANS. 

Classification,  groups  subordinate  to  groups — Natural  system — 
Rules  and  difficulties  in  classification,  explained  on  the 
theory  of  descent  with  modification — Classification  of  varie¬ 
ties — Descent  always  used  in  classification — Analogical  or 
adaptive  characters — Affinities,  general,  complex  and  radiat¬ 
ing — Extinction  separates  and  defines  groups — Morphology, 
between  members  of  the  same  class,  between  parts  of  the 
same  individual — Embryology,  laws  of,  explained  by  varia¬ 
tions  not  supervening  at  an  early  age,  and  being  inherited 
at  a  corresponding  age — Rudimentary  organs,  their  origin 
explained — Summary . 428 


CHAPTER  XV. 

RECAPITULATION  AND  CONCLUSION. 

Recapitulation  of  the  objections  to  the  theory  of  Natural  Selec¬ 
tion — Recapitulation  of  the  general  and  special  circum¬ 
stances  in  its  favor — Causes  of  the  general  belief  in  the 
immutability  of  species — How  far  the  theory  of  Natural 
Selection  may  be  extended — Effects  of  its  adoption  on 


the  study  of  Natural  History — Concluding  remarks . 476 

Glossary  of  Scientific  Terms . . . . . 507 


521 


Index 


ORIGIN  OF  SPECIES. 


INTRODUCTION. 

Wheh  on  board  H.  M.  S.  Beagle,  as  naturalist,  I  was 
much  struck  with  certain  facts  in  the  distribution  of 
the  organic  beings  inhabiting  South  America,  and  in  the 
geological  relations  of  the  present  to  the  past  inhabitants 
of  that  continent.  These  facts,  as  will  be  seen  in  the  latter 
chapters  of  this  volume,  seemed  to  throw  some  light  on  the 
'  origin  of  species — that  mystery  of  mysteries,  as  it  has  been 
called  by  one  of  our  greatest  philosophers.  On  my  return 
home,  it  occurred  to  me,  in  1837,  that  something  might 
perhaps  be  made  out  on  this  question  by  patiently  accumu¬ 
lating  and  reflecting  on  all  sorts  of  facts  which  could  possi¬ 
bly  have  any  bearing  on  it.  After  five  years’  work  I 
allowed  myself  to  speculate  on  the  subject,  and  drew  up 
some  short  notes;  these  I  enlarged  in  1844  into  a  sketch  of 
the  conclusions,  which  then  seemed  to  me  probable:  from 
that  period  to  the  present  day  I  have  steadily  pursued  the 
same  object.  I  hope  that  I  may  be  excused  for  entering 
on  these  personal  details,  as  I  give  them  to  show  that  I 
have  not  been  hasty  in  coming  to  a  decision. 

My  work  is  now  (1859)  nearly  finished;  but  as  it  will 
take  me  many  more  years  to  complete  it,  and  as  my  health 
is  far  from  strong,  I  have  been  urged  to  publish  this  ab¬ 
stract.  I  have  more  especially  been  induced  to  do  this,  as 
Mr.  Wallace,  who  is  now  studying  the  natural  history  of 
the  Malay  Archipelago,  has  arrived  at  almost  exactly  the 
same  general  conclusions  that  I  have  on  the  origin  of 
species.  In  1858  he  sent  me  a  memoir  on  this  subject, 
with  a  request  that  I  would  forward  it  to  Sir  Charles  Lyell, 
who  sent  it  to  the  Linnean  Society,  and  it  is  published  in  the 
third  volume  of  the  Journal  of  that  Society.  Sir  C.  Lyell 


2 


INTRODUCTION. 


and  Dr.  Hooker,  who  both  knew  of  my  work — the  latter 
having  read  my  sketch  of  1844 — honored  me  by  thinking 
it  advisable  to  publish,  with  Mr.  Wallace’s  excellent  memoir, 
some  brief  extracts  from  my  manuscripts. 

This  abstract,  which  I  now  publish,  must  necessarily  be 
imperfect.  I  cannot  here  give  references  and  authorities 
for  my  several  statements;  and  I  must  trust  to  the  reader 
reposing  some  confidence  in  my  accuracy.  No  doubt  errors 
may  have  crept  in,  though  I  hope  I  have  always  been  cau¬ 
tious  in  trusting  to  good  authorities  alone.  I  can  here  give 
only  the  general  conclusions  at  which  I  have  arrived,  with 
a  few  facts  in  illustration,  but  which,  I  hope,  in  most  cases 
will  suffice.  No  one  can  feel  more  sensible  than  I  do  of 
the  necessity  of  hereafter  publishing  in  detail  all  the  facts, 
with  references,  on  which  my  conclusions  have  been 
grounded;  and  I  hope  in  a  future  work  to  do  this.  For 
I  am  well  aware  that  scarcely  a  single  point  is  discussed  in 
this  volume  on  which  facts  cannot  be  adduced,  often  ap¬ 
parently  leading  to  conclusions  directly  opposite  to  those 
at  which  I  have  arrived.  A  fair  result  can  be  obtained 
only  by  fully  stating  and  balancing  the  facts  and  arguments 
on  both  sides  of  eacii  question;  and  this  is  here  impossible. 

I  much  regret  that  want  of  space  prevents  my  having 
the  satisfaction  of  acknowledging  the  generous  assistance 
which  I  have  received  from  very  many  naturalists,  some 
of  them  personally  unknown  to  me.  I  cannot,  however, 
let  this  opportunity  pass  without  expressing  my  deep 
obligations  to  Dr.  Hooker,  who,  for  the  last  fifteen  years, 
has  aided  me  in  every  possible  way  by  his  large  stores  of 
knowledge  and  his  excellent  judgment. 

In  considering  the  origin  of  species,  it  is  quite  conceiv¬ 
able  that  a  naturalist,  reflecting  on  the  mutual  affinities  of 
organic  beings,  on  their  embryological  relations,  their 
geographical  distribution,  geological  succession,  and  other 
such  facts,  might  come  to  the  conclusion  that  species  had 
not  been  independently  created,  but  had  descended,  like 
varieties,  from  other  species.  Nevertheless,  such  a  con¬ 
clusion,  even  if  well  founded,  would  be  unsatisfactoiy,  until 
it  could  be  shown  how  the  innumerable  species,  inhabit¬ 
ing  this  world  have  been  modified,  so  as  to  acquire  that 
perfection  of  structure  and  coadaptation  which  justly 
excites  our  admiration.  Naturalists  continually  refer  to 


INTRODUCTION. 


3 


external  conditions,  sucli  as  climate,  food,  etc.,  as  the  only 
possible  cause  of  variation.  In  one  limited  sense,  as  we 
shall  hereafter  see,  this  may  he  true;  but  it  is  preposterous 
to  attribute  to  mere  external  conditions,  the  structure,  for 
instance,  of  the  woodpecker,  with  its  feet,  tail,  beak  and 
tongue,  so  admirably  adapted  to  catch  insects  under  the 
bark  of  trees.  In  the  case  of  the  mistletoe,  which  draws 
its  nourishment  from  certain  trees,  which  has  seeds  that 
must  be  transported  by  certain  birds,  and  which  has  flowers 
with  separate  sexes  absolutely  requiring  the  agency  of  cer¬ 
tain  insects  to  bring  pollen  from  one  flower  to  the  other,  it 
is  equally  preposterous  to  account  for  the  structure  of  this 
parasite,  with  its  relations  to  several  distinct  organic 
beings,  by  the  effects  of  external  conditions,  or  of  habit,  or 
of  the  volition  of  the  plant  itself. 

It  is,  therefore,  of  the  highest  importance  to  gain  a  clear 
insighi-into  the  means  of  modification  and  coadaptation. 
At  the  commencement  of  my  observations  it  seemed  to  me 
probable  that  a  careful  study  of  domesticated  animals  and 
of  cultivated  plants  would  offer  the  best  chance  of  making 
out  this  obscure  problem.  Nor  have  I  been  disappointed; 
in  this  and  in  all  other  perplexing  cases  I  have  invariably 
found  that  our  knowledge,  imperfect  though  it  be,  of  vari¬ 
ation  under  domestication,  afforded  the  best  and  safest 
clue.  I  may  venture  to  express  my  conviction  of  the  high 
value  of  such  studies,  although  they  have  been  very  com¬ 
monly  neglected  by  naturalists. 

From  these  considerations,  I  shall  devote  the  first  chap¬ 
ter  of  this  abstract  to  variation  under  domestication.  We 
shall  thus  see  that  a  large  amount  of  hereditary  modifica¬ 
tion  is  at  least  possible;  and,  what  is  equally  or  more  im¬ 
portant,  we  shall  see  how  great  is  the  power  of  man  in 
accumulating  by  his  selection  successive  slight  variations. 
I  will  then  pass  on  to  the  variability  of  species  in  a  state  of 
nature;  but  I  shall,  unfortunately,  be  compelled  to  treat 
this  subject  far  too  briefly,  as  it  can  be  treated  properly 
only  by  giving  long  catalogues  of  facts.  We  shall,  how¬ 
ever,  be  enabled  to  discuss  what  circumstances  are  most 
favorable  to  variation.  In  the  next  chapter  the  strug¬ 
gle  for  existence  among  all  organic  beings  throughout 
the  world,  which  inevitably  follows  from  the  high  geomet¬ 
rical  ratio  of  their  increase,  will  be  considered.  This  is 


4 


INTRODUCTION. 


« 

the  doctrine  of  Malthus,  applied  to  the  whole  animal  and 
vegetable  kingdoms.  As  many  more  individuals  of  each 
species  are  horn  than  can  possibly  survive;  and  as,  conse¬ 
quently,  there  is  a  frequently  recurring  struggle  for  exist¬ 
ence,  it  follows  that  any  being,  if  it  vary  however  slightly 
in  any  manner  profitable  to  itself,  under  the  complex  and 
sometimes  varying  conditions  of  life,  will  have  a  better 
chance  of  surviving,  and  thus  be  naturally  selected.  From 
the  strong  principle  of  inheritance,  any  selected  variety 
will  tend  to  propagate  its  new  and  modified  form. 

This  fundamental  subject  of  natural  selection  will  be 
treated  at  some  length  in  the  fourth  chapter;  and  we  shall 
then  see  how  natural  selection  almost  inevitably  causes 
much  extinction  of  the  less  improved  forms  of  life,  and 
leads  to  what  I  have  called  divergence  of  character.  In  the 
next  chapter  I  shall  discuss  the  complex  and  little  known 
laws  of  variation.  In  the  five  succeeding  chapters,  the 
most  apparent  and  gravest  difficulties  in  accepting  the 
theory  will  be  given:  namely,  first,  the  difficulties  of  tran¬ 
sitions,  or  how  a  simple  being  or  a  simple  organ  can  be 
changed  and  perfected  into  a  highly  developed  being  or 
into  an  elaborately  constructed  organ;  secondly,  the  sub¬ 
ject  of  instinct,  or  the  mental  powers  of  animals;  thirdly, 
hybridism,  or  the  infertility  of  species  and  the  fertility  of 
varieties  when  intercrossed;  and  fourthly,  the  imperfection 
of  the  geological  record.  In  the  next  chapter  I  shall  con¬ 
sider  the  geological  succession  of  organic  beings  through¬ 
out  time;  in  the  twelfth  and  thirteenth,  their  geographical 
distribution  throughout  space;  in  the  fourteenth,  their 
classification  or  mutual  affinities,  both  when  mature  and 
in  an  embryonic  condition.  In  the  last  chapter  I  shall 
give  a  brief  recapitulation  of  the  whole  work,  and  a  few 
concluding  remarks. 

No  one  ought  to  feel  surprise  at  much  remaining  as  yet 
unexplained  in  regard  to  the  origin  of  species  and  varieties, 
if  he  make  due  allowance  for  our  profound  ignorance  in 
regard  to  the  mutual  relations  of  the  many  beings  which 
live  around  us.  Who  can  explain  why  one  species  ranges 
widely  and  is  very  numerous,  and  why  another  allied  species 
has  a  narrow  range  and  is  rare?  Yet  these  relations  are  of 
the  highest  importance,  for  they  determine  the  present 
welfare  and,  as  I  believe,  the  future  success  and  modifica- 


INTRODUCTION. 


5 


tion  of  every  inhabitant  of  this  world.  Still  less  do  we 
know  of  the  mutual  relations  of  the  innumerable  inhab¬ 
itants  of  the  world  during  the  many  past  geological  epochs 
in  its  history*  Although  much  remains  obscure,  and  will 
long  remain  obscure,  I  can  entertain  no  doubt,  after  the 
most  deliberate  study  and  dispassionate  judgment  of  which 
I  am  capable,  that  the  view  which  most  naturalists  until 
Tecently  entertained,  and  which  I  formerly  entertained — 
namely,  that  each  species  has  been  independently  created 
— is  erroneous.  I  am  fully  convinced  that  species  are  not 
immutable;  but  that  those  belonging  to  what  are  called  the 
same  genera  are  lineal  descendants  of  some  other  and 
generally  extinct  species,  in  the  same  manner  as  the 
acknowledged  varieties  of  any  one  species  are  the  descend¬ 
ants  of  that  species.  Furthermore,  I  am  convinced  that 
natural  selection  has  been  the  most  important,  but  not  the 
exclusive,  means  of  modification* 


VARIATION  UNDER  DOMESTICATION. 


6 


CHAPTER  L 

VARIATION'  UNDER  DOMESTICATION. 

Causes  of  Variability — Effects  of  Habit  and  tbe  use  or  disuse  of 
Parts — Correlated  Variation — Inheritance — Character  of  Domes¬ 
tic  Varieties — Difficulty  of  distinguishing  between  Varieties 
and  Species — Origin  of  Domestic  Varieties  from  one  or  more 
Species — Domestic  Pigeons,  their  Differences  and  Origin — 
Principles  of  Selection,  anciently  followed,  their  Effects — 
Methodical  and  Unconscious  Selection — Unknown  Origin  of 
our  Domestic  Productions — Circumstances  favorable  to  Man’s 
power  of  Selection. 

CAUSES  OF  VARIABILITY. 

When  we  compare  tbe  individuals  of  the  same  variety 
or  sub-variety  of  our  older  cultivated  plants  and  animals, 
one  of  the  first  points~which  strikes  us  is,  that  they  gen¬ 
erally  differ  more  from  each  other  than  do  the  individuals  , 
of  any  one  species  or  variety  in  a  state  of  nature.  And  if 
we  reflect  on  the  vast  diversity  of  the  plants  and  animals 
which  have  been  cultivated,  and  which  have  varied  during 
all  ages  under  the  most  different  climates  and  treatment, 
we  are  driven  to  conclude  that  this^ceat  variability  is  due 
to  our  domestic  productions  having  been  raised  under  corr- 
cUfibns  of  life  nbiT  so  uniform  as,  and  somewhat  different 
Tron^HEImse  towhich,the  parent  species  had  been  exposed 
under  nature.  There  is,  also,  some  probability  in  the  view 
propounded  by  Andrew  Knight,  that  this  variability  may 
be  partly  connected  with  excess  of  food.  It  seems  clear 
thatorgamc  beings  musITbe  exposed~cluring  several  gener¬ 
ations  to  new  conditions  to  cause  any  great  amount  of 
variation;  and  that,  when  the  organization  has  once  begun 
to  vary,  it  generally  continues  varying  for  many  gener¬ 
ations.  No  case  is  on  record  of  a  variable  organism  ceas¬ 
ing  to  vary  under  cultivation.  Our  oldest  cultivated 
plants,  such  as  wheat,  still  yield  new  varieties:  our  oldest 


VARIATION  UNDER  DOMESTICATION. 


domesticated  animals  are  still  capable  of  rapid  improve¬ 
ment  or  modification 

As  far  as  I  am  able  to  judge,  after  long  attending  to  the 
subject,  the  conditions  of  life  appear  to  act  in  two  ways — 
directly  on  the  whole  organization  or  on  certain  parts 
alon$  and  indirectly  by  affecting  the  reproductive  system. 
With  respect  to  the  direct  action,  we  must  bear  in  mind 
that  in  every  case,  as  Professor  Weismann  has  lately 
insisted,  and  as  I  have  incidently  shown  in  my  work  on 
“  Variation  under  Domestication,”  there  are  two  factors: 
namely,  the  nature  of  the  organism  and  the  nature  of  the 
conditions.  The  former  seems  to  be  much  the  more 
important;  for  nearly  similar  variations  sometimes  arise 
under,  as  far  as  we  can  judge,  dissimilar  conditions;  and, 
on  the  other  hand,  dissimilar  variations  arise  under  condi¬ 
tions  which  appear  to  be  nearly  uniform.  The  effects  on 
the  offspring  ^ire,,either  definite  or  indefinite.  They  may 
be  considered  as  definite  widen  all  or  nearly  all  the  offspring 
of  individuals  exposed  to  certain  conditions  during  several 
generations  are  modified  in  the  same  manner.  It  is 
extremely  difficult  to  comeTttT  any  conclusion  in  regard  to 
the  extent  of  the  changes  which  have  been  thus  definitely 
induced.  There  can,  however,  be  little  doubt  about  many 
slight  changes,  such  as  size  from  the  amount  of  food, 
color  from  the  nature  of  the  food,  thickness  of  the  skin 
and  hair  from  climate,  etc.  Each  of  the  endless  variations 
which  we  see  in  the  plumage  of  our  fowls  must  have  had 
some  efficient  cause;  and  if  the  same  cause  were  to  act 
uniformly  during  a  long  series  of  generations  on  many 
individuals,  all  probably  would  be  modified  in  the  same 
manner.  Such  facts  as  the  complex  and  extraordinary 
outgrowths  which  variably  follow  from  the  insertion  of  a 
minute  drop  of  poison  by  a  gall-producing  insect,  shows  us 
what  singular  modifications  might  result  in  the  case  of 
plants  from  a  chemical  change  in  the  nature  of  the  sap. 

Indefinite  variability  is  a  much  more  common  result  of 
changed  conditions  than  definite  variability,  and  has  prob¬ 
ably  played  a  more  important  part  in  the  formation  of  our 
domestic  races.  We  see  indefinite  variability  in  the  end¬ 
less  slight  peculiarities  which  distinguish  the  individuals 
of  the  same  species,  and  which  cannot  be  accounted  for  by 
inheritance  from  either  parent  or  from  some  more  remote 


VARIATION  UNDER  DOMESTICATION. 


& 

ancestor.  Even  strongly-marked  differences  occasionally 
appear  in  tlio  young  of  the  same  litter,  and  in  seedlings 
from  the  same  seed-capsule.  At  long  intervals  of  time, 
out  of  millions  of  individuals  reared  in  the  same  country 
and  fed  on  nearly  the  same  food,  deviations  of  structure  so 
strongly  pronounced  as  to  deserve  to  be  called  monstros¬ 
ities  arise;  but  monstrosities  cannot  be  separated  by  any 
distinct  line  from  slighter  variations.  All  such  changes  of 
structure,  whether  extremely  slight  or  strongly  marked, 
which  appear  among  many.Jndividuals  Jiving— together.— 
may  be  considered__as  the  indefinite  effects  of  the  non  dic¬ 
tions  of  life  on  each  individual  organism^  m-mearly  the 
same  mannei_asJflte- -chillr-effects-di ffereni-men-  inanindefi- 
nite  manner,  according-io  their  state  of  body  or  constitu - 
tion.  causing  coughs^or  colds,  rheu mutism ,  or  inflammation 
of  yarimifr-orgahsT 

IVitli  respect  to  what  I  have  called  the  indirect  action  of 
changed  conditions,  namely,  through  the  reproductive 
system  of  being  affected,  we  may  infer  that  variability  is 
thus  induced,  partly  from  the  fact  of  this  system  being 
extremely  sensitive  to  any  change  in  the  conditions,  and 
partly  from  the  similarity,  as  Kolreuter  and  others  have 
remarked,  between  the  variability  which  follows  from  the 
srossing  of  distinct  species,  and  that  which  may  be  observed 
with  plants  and  animals  when  reared  under  new  or  unnat¬ 
ural  conditions.  Many  facts  clearly  show  how  eminently 
susceptible  the  reproductive  system  is  to  very  slight 
changes  in  the  surrounding  conditions.  Nothing  is  more 
easy  than  to  tame  an  animal,  and  few  things  more  difficult 
than  to  get  it  to  breed  freely  under  confinement,  even  when 
the  male  and  female  unite.  How  many  animals  there  are 
which  will  not  breed,  though  kept  in  an  almost  free  state  in 
their  native  country!  This  is  generally,  but  erroneously 
attributed  to  vitiated  instincts.  Many  cultivated  plants 
display  the  utmost  vigor,  and  yet  rarely  or  never  seed!  In 
some  few  cases  it  has  been  discovered  that  a  very 
trifling  change,  such  as  a  little  more  or  less  water  at 
some  particular  period  of  growth,  will  determine  whether 
or  not  a  plant  will  produce  seeds.  I  cannot  here  give  the 
details  which  I  have  collected  and  elsewhere  published 
on  this  curious  subject;  but  to  show  how  singular  the 
laws  are  which  determine  the  reproduction  of  animals 


VARIATION  UNDER  DOMESTICATION. 


9 


under  confinement,  I  may  mention  that  carnivorous 
animals,  even  from  the  tropics,  breed  in  this  country 
pretty  freely  under  confinement,  with  the  exception  of  the 
plantigrades  or  bear  family,  which  seldom  produce  young; 
whereas  carnivorous  birds,  with  the  rarest  exception,  hardly 
ever  lay  fertile  eggs.  Many  exotic  plants  have  pollen 
utterly  worthless,  in  the  same  condition  as  in  the  most 
sterile  hybrids.  When,  on  the  one  hand,  we  see  domesti¬ 
cated  animals  and  plants,  though  often  weak  and  sickly, 
breeding  freely  under  confinement;  and  when,  on  the  other 
hand,  we  see  individuals,  though  taken  young  from  a  state 
of  nature  perfectly  tamed,  long-lived  and  healthy  ( of 
which  I  could  give  numerous  instances),  yet  having  their 
reproductive  system  so  seriously  affected  by  unperceived 
causes  as  to  fail  to  act,  we  need  not  be  surprised  at  this 
system,  when  it  does  act  under  confinement,  acting  irregu¬ 
larly,  and  producing  offspring  somewhat  unlike  their 
parents.  I  may  add  that  as  some  organisms  breed  freely 
under  the  most  unnatural  conditions — for  instance,  rabbits 
and  ferrets  kept  in  hutches — showing  that  their  reproduct¬ 
ive  organs  are  not  easily  affected;  so  will  some  animals  and 
plants  withstand  domestication  or  cultivation,  and  vary 
very  slightly — perhaps  hardly  more  than  in  a  state  of 
nature. 

Some  naturalists  have  maintained  that  all  variations  are 
connected  with  the  act  of  sexual  reproduction;  but  this  is 
certainly  an  error;  for  I  have  given  m  another  work  a  long 
list  of  “  sporting  plants,”  as  they  are  called  by  gardeners; 
that  is,  of  plants  which  have  suddenly  produced  a  single 
bud  with  a  new  and  sometimes  widely  different  character 
from  that  of  the  other  buds  on  the  same  plant.  These 
bud  variations,  as  they  may  be  named,  can  be  propagated 
by  grafts,  offsets,  etc.,  and  sometimes  by  seed.  They 
©ccur  rarely  under  nature,  but  are  far  from  rare  under 
culture.  As  a  single  bud  out  of  many  thousands  produced 
year  after  year  on  the  same  tree  under  uniform  conditions, 
has  been  known  suddenly  to  assume  a  new  character;  and 
as  buds  on  distinct  trees,  growing  under  different  con¬ 
ditions,  have  sometimes  yielded  nearly  the  same  variety — 
for  instance,  buds  on  peach-trees  producing  nectarines, 
and  buds  on  common  roses  producing  moss-roses — we 
clearly  see  that  the  nature  of  the  conditions  is  of  subordi- 


10 


VARIATION  UNDER  DOMESTICATION. 


nate  importance  in  comparison  with  the  nature  of  the 
organism  in  determining  each  particular  form  of  varia¬ 
tion;  perhaps  of  not  more  importance  than  the  nature  of 
the  spark,  by  which  a  mass  of  combustible  matter  is 
ignited,  has  in  determining  the  nature  of  the  flames. 

effects  of  habit  and  of  the  use  or  disuse  of  parts; 

CORRELATED  VARIATION;  INHERITANCE. 

Changed  habits  produce  an  inherited  effect  as  in  the 
period  of  the  flowering  of  plants  when  transported  from 
one  climate  to  another.  With  animals  the  increased 
use  or  disuse  of  parts  has  had  a  more  marked  influence; 
thus  I  find  in  the  domestic  duck  that  the  bones  of  the 
wing  weigh  less  and  the  bones  of  the  leg  more,  in 
proportion  to  the  whole  skeleton,  than  do  the  same 
bones  in  the  wild  duck;  and  this  change  may  be 
safely  attributed  to  the  domestic  duck  flying  much 
less,  and  walking  more,  than  its  wild  parents.  The 
great  and  inherited  development  of  the  udders  in  cows 
and  goats  in  countries  where  they  are  habitually  milked,  in 
comparison  with  these  organs  in  other  countries,  is  prob¬ 
ably  another  instance  of  the  effects  of  use.  Not  one  of  our 
domestic  animals  can  be  named  which  has  not  in  some 
country  drooping  ears;  and  the  view  which  has  been  sug¬ 
gested  that  the  drooping  is  due  to  disuse  of  the  muscles'  of 
the  ear,  from  the  animals  being  seldom  much  alarmed, 
seems  probable. 

Many  laws  regulate  variation,  some  few  of  which  can  be 
dimly  seen,  and  will  hereafter  be  briefly  discussed.  I  will 
here  only  allude  to  what  may  be  called  correlated  variation. 
Important  changes  in  the  embryo  or  larva  will  probably 
entail  changes  in  the  mature  animal.  In  monstrosities,  the 
correlations  between  quite  distinct  parts  are  very  curious; 
and  many  instances  are  given  in  Isidore  Geoffroy  St. 
Hilaire's  great  work  on  this  subject.  Breeders  believe  that 
long  limbs  are  almost  always  accompanied  by  an  elongated 
head.  Some  instances  of  correlation  are  quite  whimsical;  • 
thus  cats  which  are  entirely  white  and  have  blue  eyes  are 
generally  deaf;  but  it  has  been  lately  stated  by  Mr.  Tait 
that  this  is  confined  to  the  males.  Color  and  constitu¬ 
tional  pecularities  go  together,  of  which  many  remarkable 


VARIATION  UNDER  DOMESTICATION. 


11 


cases  could  be  given  among  animals  and  plants.  From 
facts  collected  by  Heusinger,  it  appears  that  white  sheep  1 
and  pigs  are  injured  by  certain  plants,  while  dark-colored 
individuals  escape:  Professor  Wyman  has  recently  com¬ 
municated  to  me  a  good  illustration  of  this  fact;  on  asking 
some  farmers  in  Virginia  how  it  was  that  all  their  pigs  were 
black,  they  informed  him  that  the  pigs  ate  the  paint-root 
(Lachnanthes),  which  colored  their  bones  pink,  and  which 
caused  the  hoofs  of  all  but  the  black  varieties  to  drop  off; 
and  one  of  the  “  crackers  ”  ( i .  e.  Virginia  squatters)  added, 

“  we  select  the  black  members  of  a  litter  for  raising,  as 
they  alone  have  a  good  chance  of  living.”  Hairless  dogs 
have  imperfect  teeth;  long-haired  and  coarse-haired  animals 
are  apt  to  have,  as  is  asserted,  long  or  many  horns;  pigeons 
with  feathered  feet  have  skin  between  their  outer  toes; 
pigeons  with  short  beaks  have  small  feet,  and  those  with 
long  beaks  large  feet.  Hence  if  man  goes  on  selecting,\ 
and  thus  augmenting,  any  peculiarity,  he  will  almost  cer-l 
tainly  modify  unintentionally  other  parts  of  the  structure/ 
owing  to  the  mysterious  laws  of  correlation. 

The  results  of  the  various,  unknown,  or  but  dimly 
understood  laws  of  variation  are  infinitely  complex  and 
diversified.  It  is  well  worth  while  carefully  to  study  the 
several  treatises  on  some  of  our  old  cultivated  plants,  as  on 
the  hyacinth,  potato,  even  the  dahlia,  etc. ;  and  it  is  really 
sui  prising  to  note  the  endless  points  of  structure  and  con¬ 
stitution  in  which  the  varieties  and  sub-varieties  differ 
slightly  from  each  other.  The  whole  organization  seems  to 
have  become  plastic,  and  departs  in  a  slight  degree  from 
that  of  the  parental  type. 

Any  variation  which  is  not  inherited  is  unimportant  for 
us.  But  the  number  and  diversity  of  inheritable  deviations 
of  structure,  both  those  of  slight  and  those  of  consider¬ 
able  physiological  importance,  are  endless.  Dr.  Prosper 
Lucas*  treatise,  in  two  large  volumes,  is  the  fullest 
and  the  best  on  this  subject.  Ho  breeder  doubts  how 
strong  is  the  tendency  to  inheritance;  -that  like  pro¬ 
duces  like  is  his  fundamental  belief :  doubts  have 
been  thrown  on  this  principle  only  by  theoretical 
writers.  When  any  deviation  of  structure  often  appears, 
and  we  see  it  in  the  father  and  child,  we  cannot  tell 
whether  it  may  not  be  due  to  the  same  o&use  having  acted 


12 


VARIATION  UNDER  DOMESTICATION. 


on  both;  but  when  among  individuals,  apparently  exposed 
to  the  same  conditions,  any  very  rare  deviation,  due  to 
some  extraordinary  combination  of  circumstances,  appeals 
in  the  parent — say,  once  among  several  million  individu¬ 
als — and  it  reappears  in  the  child,  the  mere  doctrine  of 
chances  almost  compels  us  to  attribute  its  reappearance  to 
inheritance.  Every  one  must  have  heard  of  cases  of  al¬ 
binism,  prickly  skin,  hairy  bodies,  etc.,  appearing  in 
several  members  of  the  same  family.  If  strange  and  rare  de¬ 
viations  of  structure  are  really  inherited,  less  strange  and 
commoner  deviations  may  be  freely  admitted  to  be  inherit¬ 
able.  Perhaps  the  correct  way  of  viewing  the  whole 
subject  would  be,  to  look  at  the  inheritance  of  every 
character  whatever  as  the  rule,  and  non-inheritance  as  the 
anomaly. 

The  Jaws  governing  inheritance. ..  are  for  the  most  part 
unknown.  NcT  one  canTsay  why  the  same  peculiarity  in 
'different  individuals  of  the  same  species,  or  in  different 
species,  is  sometimes  inherited  and  sometimes  not  S03  why 
the  child  often  reverts  in  certain  characteristics  to  its  grand¬ 
father  or  grandmother  or  more  remote  ancestor;  why  a 
peculiarity  is  often  transmitted  from  one  sex  to  both  sexes, 
or  to  one  sex  alone,  more  commonly  but  not  exclusively  to 
the  like  sex.  It  is  a  fact  of  some  importance  to  us,  that 
peculiarities  appearing  in  the  males  of  our  domestic  breeds 
are  often  transmitted,  either  exclusively  or  in  a  much 
greater  degree,  to  the  males  alone.  A  much  more  im¬ 
portant  rule,  which  I  think  may  be  trusted,  is  that,  at 
whatever  period  of  life  a  peculiarity  first  appears,  it  tends 
to  reappear  in  the  offspring  at  a  corresponding  age,  though 
sometimes  earlier.  In  many  cases  this  could  not  be  other¬ 
wise;  thus  the  inherited  peculiarities  in  the  horns  of  cattle 
could  appear  only  in  the  offspring  when  nearly  mature; 
peculiarities  in  the  silk-worm  are  known  to  appear  at  the 
corresponding  caterpillar  or  cocoon  stage.  But  hereditary 
diseases  and  some  other  facts  make  me  believe  that  the 
rule  has  a  wider  extension,  and  that,  when  there  is  no  ap¬ 
parent  reason  why  a  peculiarity  should  appear  at  any 
particular  age,  yet  that  it  does  tend  to  appear  in  the  off¬ 
spring  at  the  same  period  at  which  it  first  appeared  in  the 
parent.  I  believe  this  rule  to  be  of  the  highest  importance 
in  explaining  the  laws  of  embryology.  These  remarks  are 


VARIATION  UNDER  DOMESTICATION. 


13 


of  course  confined  to  the  first  appearance  of  the  peculiarity, 
and  not  to  the  primary  cause  which  may  have  acted  on  the 
ovules  or  on  the  male  element;  in  nearly  the  same  manner 
as  the  increased  length  of  the  horns  in  the  offspring  fron 
a  short-horned  cow  by  a  long-horned  bull,  though  appear¬ 
ing  late  in  life,  is  clearly  due  to  the  male  element. 

Having  alluded  to  the  subject  of  reversion,  I  may  here 
refer  to  a  statement  often  made  by  naturalists — namely, 
that  our  domestic  varieties,  when  run  wild,  gradually  but 
invariably  revert  in  character  to  their  aboriginal  stocks. 
Hence  it  has  been  argued  that  "nolleductions  can  be  drawn 
from  domestic  races  to  species  in  a  state  of  nature.  I  have 
in  vain  endeavored  to  discover  on  what  decisive  facts 
the  above  statement  has  so  often  and  so  boldly  been  made. 
There  would  be  great  difficulty  in  proving  its  truth:  we 
may  safely  conclude  that  very  many  of  the  most  strongly 
marked  domestic  varieties  could  not  possibly  live  in  a  wild 
state.  In  many  cases  we  do  not  know  what  the  aboriginal 
stock  was,  and  so  could  not  tell  whether  or  not  nearly  per¬ 
fect  reversion  had  ensued.  It  would  be  necessary,  in  order 
to  prevent  the  effects  of  intercrossing,  that  only  a  single 
variety  should  have  been  tuFned  loose  in  its  new  home. 
Nevertheless,  as  our  varieties  certainly  do  occasionally 
revert  in  some  of  their  characters  to  ancestral  forms,  it 
seems  to  me  not  improbable  that  if  we  could  succeed  in 
naturalizing,  or  were  to  cultivate,  during  many  gener¬ 
ations,  the  several  races,  for  instance,  of  the  cabbage,  in 
very  poor  soil — in  which  case,  however,  some  effect  would 
have  to  be  attributed  to  the  definite  action  of  the  poor 
soil — that  they  would,  to  a  large  extent,  or  even  wholly, 
revert  to  the  wild  aboriginal  stock.  Whether  or  not  the 
experiment  would  succeed  is  not  of  great  importance  for 
our  line  of  argument;  for  by  the  experiment  itself  the 
conditions  of  life  are  changed.  If  it  could  be  shown  that 
our  domestic  varieties  manifested  a  strong  tendency  to 
reversion — that  is,  to  lose  their  acquired  characters,  while 
kept  under  the  same  conditions  and  while  kept  in  a  con¬ 
siderable  body,  so  that  free  intercrossing  might  check,  by 
blending  together,  any  slight  deviations  in  their  structure, 
in  such  case,  I  grant  that  we  could  deduce  nothing  from 
domestic  varieties  in  regard  to  species.  But  there  is  not  a 
shadow  of  evidence  in  favor  of  this  view:  to  assert  that  we 


14 


CHARACTER  OF  DOMESTIC  VARIETIES, 


could  not  breed  our  cart  and  race-horses,  long  and  short¬ 
horned  cattle,  and  poultry  of  various  breeds,  and  esculent 
vegetables,  for  an  unlimited  number  of  generations,  would 
be  opposed  to  all  experience. 

CHARACTER  OF  DOMESTIC  VARIETIES;  DIFFICULTY  OF  DIS¬ 
TINGUISHING  BETWEEN  VARIETIES  AND  SPECIES ; 
ORIGIN  OF  DOMESTIC  VARIETIES  FROM  ONE  OR  MORE 
SPECIES. 

"When  we  look  to  the  hereditary  varieties  or  races  of  our 
domestic  animals  and  plants,  and  compare  them  with 
closely  allied  species,  we  generally  perceive  in  each  domes¬ 
tic  race,  as  already  remarked,  less  uniformity  of  character 
than  in  true  species.  Domestic  races  often  have  a  some¬ 
what  monstrous  character ;  by  which  I  mean,  that, 
although  differing  from  each  other  and  from  other  species 
of  the  same  genus,  in  several  trifling  respects,  they  often 
differ  in  an  extreme  degree  in  some  one  part,  both  when 
compared  one  with  another,  and  more  especially  when 
compared  with  the  species  under  nature  to  which  they  are 
nearest  allied.  With  these  exceptions  (and  with  that  of 
the  perfect  fertility  of  varieties  when  crossed — a  subject 
hereafter  to  be  discussed), /domestic  races  of  the  same 
species  differ  from  each  other  in  the  same  manner  as  do 
the  closely  allied  species  of  the  same  genus  in  a  state  of 
nature,  but  the  differences  in  most  cases  are  less  in  degree. 
This  must  be  admitted  as  true,  for  the  domestic  races  of 
many  animals  and  plants  have  been  ranked  by  some  com¬ 
petent  judges  as  the  descendants  of  aboriginally  distinct 
species,  and  by  other  competent  judges  as  mere  varieties. 
If  any  well  marked  distinction  existed  between  a  domestic 
race  and  a  species,  this  source  of  doubt  would  not  so  per¬ 
petually  recur.  It  has  often  been  stated  that  domestic  races 
do  not  differ  ft'om  each  other  in  characters  of  generic  value. 
It  can  be  shown  that  this  statement  is  not  correct;  but 
naturalists  differ  much  in  determing  what  characters  are 
of  generic  value;  all  such  valuations  being  at  present 
empirical.  When  it  is  exjffained  how  genera  originate 
under  nature,  it  will  be  seen  that  we  have  no  right  to 
expect  often  to  find  a  generic  amount  of  difference  in  our 
domesticated  races. 


CHARACTER  OH  DOMESTIC  VARIETIES. 


15 


In  attempting  to  estimate  the  amount  of  structural  dif¬ 
ference  between  allied  domestic  races,  we  are  soon  involved 
in  doubt,  from  not  knowing  whether  they  are  descended 
from  one  or  several  parent  species.  This  point,  if  it  could 
be  cleared  up,  would  be  interesting;  if,  for  instance,  it 
could  be  shown  that  the  greyhound,  bloodhound,  terrier, 
spaniel  and  bull-dog,  which  we  all  know  propagate  their  kind 
truly,  were  the  offspring  of  any  single  species,  then  such 
facts  would  have  great  weight  in  making  us  doubt  about 
the  immutability  of  the  many  closely  allied  natural  species 
—for  instance,  of  the  many  foxes — inhabiting  the  different 
quarters  of  the  world.  I  do  not  believe,  as  we  shall  pres¬ 
ently  see,  that  the  whole  amount  of  difference  between  the 
several  breeds  of  the  dog  has  been  produced  under  domes¬ 
tication;  I  believe  that  a  small  part  of  the  difference  is  due 
to  their  being  descended  from  distinct  species.  In  the  case 
of  strongly  marked— races-  -of— gome-  other  domesticated- 
species,  there  is  presumptive  or  even  strong  evidence  that 
all  are  descended  from  a  single  wil'd  stock. 

It  has  often  been  assumed  that  man  has  chosen  for  do¬ 
mestication  animals  and  plants  having  an  extraordinary 
inherent  tendency  to  vary,  and  likewise  to  withstand 
diverse  climates.  I  do  not  dispute  that  these  capacities 
have  added  largely  to  the  value  of  most  of  our  domesticated 
productions;  but  how  could  a  savage  possibly  know,  when 
he  first  tamed  an  animal,  whether  it  would  vary  in  suc¬ 
ceeding  generations,  and  whether  it  would  endure  other 
climates?  Has  the  little  variability  of  the  ass  and  goose,  or 
the  small  power  of  endurance  of  warmth  by  the  reindeer, 
or  of  cold  by  the  common  camel,  prevented  their  domesti¬ 
cation?  I  cannot  doubt  that  if  other  animals  and  plants, 
equal  in  number  to  our  domesticated  productions,  and 
belonging  to  equally  diverse  classes  and  countries,  were 
taken  from  a  state  of  nature,  and  could  be  made  to  breed 
for  an  equal  number  of  generations  under  domestication, 
they  would  on  an  average  vary  as  largely  as  the  parent 
species  of  our  existing  domesticated  productions  have 
varied. 

In  the  case  of  most  of  our  anciently  domesticated  animals 
and  plants,  it  is  not  possible  to  come  to  any  definite  con¬ 
clusion,  whether  they  are  descended,  from  one  or  several 
wild  species.  The  argument  mainly  relied  on  by  those  who 


16 


CHARACTERS  OF  DOMESTIC  VARIETIES. 


believe  in  the  multiple  origin  of  our  domestic  animals  is, 
that  we  find  in  the  most  ancient  times,  on  the  monuments 
of  Egypt,  and  in  the  lake-habitations  of  Switzerland, 
much  diversity  in  the  breeds  ;  and  that  some  of  these 
ancient  breeds  closely  resemble,  or  are  even  identical  with, 
those  still  existing.  But  this  only  throws  far  backward 
the  history  of  civilization,  and  shows  that  animals  were 
domesticated  at  a  much  earlier  period  than  has  hitherto 
been  supposed.  The  lake-inhabitants  of  Switzerland  cul¬ 
tivated  several  kinds  of  wheat  and  barley,  the  pea,  the 
poppy  for  oil  and  flax  ;  and  they  possessed  several  domesti¬ 
cated  animals.  They  also  carried  on  commerce  with  other 
nations.  All  this  clearly  shows,  as  Ileer  has  remarked, 
that  they  had  at  this  early  age  progressed  considerably  in 
civilization  ;  and  this  again  implies  a  long  continued  pre¬ 
vious  period  of  less  advanced  civilization,  during  which  the 
domesticated  animals,  kept  by  different  tribes  in  different 
districts,  might  have  varied  and  given  rise  to  distinct  races. 
Since  the  discovery  of  flint  tools  in  the  superficial  forma¬ 
tions  of  many  parts  of  the  world,  all  geologists  believe  that 
barbarian  men  exsisted  at  an  enormously  remote  period  ; 
and  we  know  that  at  the  present  day  there  is  hardly  a  tribe 
so  barbarous  as  not  to  have  domesticated  at  least  the  dog. 

The  origin  of  most  of  our  domestic  animals  will  prob¬ 
ably  forever  remain  vague.  But  I  may  here  state  that, 
looking  to  the  domestic  dogs  of  the  whole  world,  I  have, 
after  a  laborious  collection  of  all  known  facts,  come  to  the 
conclusion  that  several  wild  species  of  Canidse  have  been 
tamed,  and  that  their  blood,  in  some  cases  mingled 
together,  flows  in  the  veins  of  our  domestic  breeds.  In 
regard  to  sheep  and  goats  I  can  form  no  decided  opinion. 
From  facts  communicated  to  me  by  Mr.  Blyth,  on  the 
habits,  voice,  constitution  and  structure  of  the  humped 
Indian  cattle,  it  is  almost  certain  that  they  are  descended 
from  a  different  aboriginal  stock  from  our  European  cattle  ; 
and  some  competent  judges  believe  that  these  latter  have 
had  two  or  three  wild  progenitors,  whether  or  not  these 
deserve  to  be  called  species.  This  conclusion,  as  well  as 
that  of  the  specific  distinction  between  the  humped  and 
common  cattle,  may,  indeed,  be  looked  upon  as  established 
by  the  admirable  researches  of  Professor  Rutimeyer.  With 
respect  to  horses,  from  reasons  which  I  cannot  here  give,  I 


CHARACTER  OF  DOMESTIC  VARIETIES. 


17 


am  doubtfully  inclined  to  believe,  in  opposition  to  several 
authors,  that  all  the  races  belong  to  the  same  species. 
Having  kept  nearly  all  the  English  breeds  of  the  fowl  alive, 
having  bred  and  crossed  them,  and  examined  their  skele¬ 
tons,  it  appears  to  me  almost  certain  that  all  are  the 
descendents  of  the  wild  Indian  fowl,  Gallus  bankiva;  and 
this  is  the  conclusion  of  Mr.  Blyth,  and  of  others  who  have 
studied  this  bird  in  India.  In  regard  to  ducks  and  rabbits, 
some  breeds  of  which  differ  much  from  each  other,  the 
evidence  is  clear  that  they  are  all  descended  from  the 
common  duck  and  wild  rabbit. 

The  doctrine  of  the  origin  of  our  several  domestic  races 
from  several  aboriginal  stocks,  has  been  carried  to  an 
absurd  extreme  by  some  authors.  They  believe  that  every 
race  which  breeds  true,  let  the  distinctive  characters  be 
ever  so  slight,  has  had  its  wild  prototype.  At  this  rate 
there  must  have  existed  at  least  a  score  of  species  of  wild 
cattle,  as  many  sheep,  and  several  goats,  in  Europe  alone, 
and  several  even  within  Great  Britain.  One  author  believes 
that  there  formerly  existed  eleven  wild  species  of  sheep 
peculiar  to  Great  Britain!  When  we  bear  in  mind  that 
Britain  has  now  not  one  peculiar  mammal,  and  France  but 
few  distinct  from  those  of  Germany,  and  so  with  Hungary, 
Spain,  etc.,  but  that  each  of  these  kingdoms  possesses  sev¬ 
eral  peculiar  breeds  of  cattle,  sheep,  etc.,  we  must  admit 
that  many  domestic  breeds  must  have  originated  in  Europe; 
for  whence  otherwise  could  they  have  been  derived?  So 
it  is  in  India.  Even  in  the  case  of  the  breeds  of  the 
domestic  dog  throughout  the  world,  which  I  admit  are 
descended  from  several  wild  species,  it  cannot  be  doubted 
that  there  has  been  an  immense  amount  of  inherited 
variation;  for  who  will  believe  that  animals  closely 
resembling  the  Italian  greyhound,  the  bloodhound,  the 
bull-dog,  pug-dog,  or  Blenheim  spaniel,  etc. — so  unlike 
all  wild  Canidse — ever  existed  in  a  state  of  nature?  It 
has  often  been  loosely  said  that  all  our  races  of  dogs  have 
been  produced  by  the  crossing  of  a  few  aboriginal  species; 
but  by  crossing  we  can  only  get  forms  in  some  degree  inter¬ 
mediate  between  their  parents;  and  if  we  account  for  our 
several  domestic  races  by  this  process,  we  must  admit  the 
former  existence  of  the  most  extreme  forms,  as  the  Italian 
greyhound,  bloodhound,  bull-dog,  etc.,  in  the  wild  state. 


18 


DOMESTIC  1  'IQ  EONS. 


Moreover,  the  possibility  of  making  distinct  races  by  cross¬ 
ing  has  been  greatly  exaggerated.  Many  cases  are  on  record 
showing  that  a  race  may  be  modified  by  occasional  crosses 
if  aided  by  the  careful  selection  of  the  individuals  which 
present  the  desired  character;  but  to  obtain  a  race  inter¬ 
mediate  between  two  quite  distinct  races  would  be  very 
difficult.  Sir  J,  Sebright  expressly  experimented  with 
this  object  and  failed.  The  offspring  from  the  first  cross 
between  two  pure  breeds  is  tolerably  and  sometimes  (as  I 
have  found  with  pigeons)  quite  uniform  in  character,  and 
every  thing  seems  simple  enough;  but  when  these  mongrels 
are  crossed  one  with  another  for  several  generations,  hardly 
two  of  them  are  alike,  and  then  the  difficulty  of  the  task 
becomes  manifest. 

BREEDS  OF  THE  DOMESTIC  PIGEON,  THEIR  DIFFERENCES 

AND  ORIGIN. 

Believing  that  it  is  always  best  to  study  some  special 
group,  I  have,  after  deliberation,  taken  up  domestic 
pigeons.  I  have  kept  every  breed  which  I  could  purchase 
or  obtain,  and  have  been  most  kindly  favored  with  skins 
from  several  quarters  of  the  world,  more  especially  by  the 
Hon.  Wo  Elliot,  from  India,  and  by  the  Hon.  C.  Murray, 
from  Persia.  Many  treatises  in  different  languages  have 
been  published  on  pigeons,  and  some  of  them  are  very 
important  as  being  of  considerable  antiquity.  I  have 
associated  with  several  eminent  fanciers  and  have  been  per¬ 
mitted  to  join  two  of  the  London  Pigeon  Clubs.  The 
|  diyexsityiof  the  breeds  is  something  astonishing.  Compare 
the  English  carrier  and  the  short-faced  tumbler,  and  see 
the  wonderful  difference  in  their  beaks,  entailing  corres¬ 
ponding  differences  in  their  skulls.  The  carrier,  more 
especially  the  male  bird,  is  also  remarkable  from  the  won¬ 
derful  development  of  the  carunculated  skin  about  the 
head;  and  this  is  accompanied  by  greatly  elongated  eyelids, 
very  large  external  orifices  to  the  nostrils,  and  a  wide  gape 
of  mouth.  The  short-faced  tumbler  has  a  beak  in  outline 
almost  like  that  of  a  finch;  and  the  common  tumbler  has 
the  singular  inherited  habit  of  flying  at  a  great  height  in  a 
compact  flock  and  tumbling  in  the  air  head  over  heels. 
The  runt  is  a  bird  of  great  with  long  massive  beak 


DOMESTIC  PIGEONS. 


19 


and  large  feet;  some  of  the  sub-breeds  of  runts  have  very 
long  necks,  others  very  long  wings  and  tails,  others  singu- 
larly  short  tails.  The  barb  is  allied  to  the  carrier,  but, 
instead  of  a  long  beak,  has  a  very  short  and  broad  one. 
The  pouter  has  a  much  elongated  body,  wings  and  legs; 
and  its  enormously  developed  crop,  which  it  glories  in 
inflating,  may  well  excite  astonishment  and  even  laughter. 
The  turbit  has  a  short  and  conical  beak  with  a  line  of 
reversed  feathers  down  the  breast;  and  it  has  the  habit  of 
continually  expanding,  slightly,  the  upper  part  of  the 
esophagus.  The  Jacobin  has  the  feathers  so  much  reversed 
along  the  back  of  the  neck  that  they  form  a  hood;  and  it  has, 
proportionally  to  its  size,  elongated  wing  and  tail  feathers. 
The  trumpeter  and  laugher,  as  their  names  express,  utter 
a  very  different  coo  from  the  other  breeds.  The  fantail 
has  thirty  or  even  forty  tail-feathers,  instead  of  twelve  or 
fourteen — the  normal  number  in  all  the  members  of  the 
great  pigeon  family:  these  feathers  are  kept  expanded  and 
are  carried  so  erect  that  in  good  birds  the  head  and  tail 
touch:  the  oil-gland  is  quite  aborted.  Several  other  less 
distinct  breeds  might  be  specified. 

In  the  skeletons  of  the  several  breeds,  the  development 
of  the  bones  of  the  face,  in  length  and  breadth  and  curva¬ 
ture,  differs  enormously.  The  shape,  as  well  as  the  breadth 
and  length  of  the  ramus  of  the  lower  jaw,  varies  in  a  highly 
remarkable  manner.  The  caudal  and  sacral  vertebra  vary 
in  number;  as  does  the  number  of  the  ribs,  together  with 
their  relative  breadth  and  the  presence  of  processes.  The 
size  and  shape  of  the  apertures  in  the  sternum  are  highly 
variable;  so  is  the  degree  of  divergence  and  relative  size  of 
the  two  arms  of  the  furcula.  The  proportional  width  of 
the  gape  of  mouth,  the  proportional  length  of  the  eye¬ 
lids,  of  the  orifice  of  the  nostrils,  of  the  tongue  (not  always 
in  strict  correlation  with  the  length  of  beak),  the  size  of 
the  crop  and  of  the  upper  part  of  the  esophagus;  the 
development  and  abortion  of  the  oil-gland;  the  number  of 
the  primary  wing  and  caudal  feathers;  the  relative  length 
of  the  wing  and  tail  to  each  other  and  to  the  body;  the 
relative  length  of  the  leg  and  foot;  the  number  of  scutelke 
on  the  toes,  the  development  of  skin  between  the  toes,  are 
all  points  of  structure  which  are  variable.  The  period  at 
which  the  perfect  plumage  is  acquired  varies,  as  does  the 


20 


DOMESTIC  PIGEONS 


state  of  the  down  with  which  the  nestling  birds  are  clothed 
when  hatched.  The  shape  and  size  of  the  eggs  vary.  The 
manner  of  flight,  and  in  some  breeds  the  voice  and  disposi¬ 
tion,  differ  remarkably.  Lastly,  in  certain  breeds,  the 
males  and  females  have  come  to  differ  in  a  slight  degree 
from  each  other. 

Altogether  at  least  a  score  of  pigeons  might  be  chosen 
which,  if  shown  to  an  ornithologist,  and  he  were  told  that 
they  were  wild  birds,  would  certainly  be  ranked  by  him  as 
well-defined  species.  Moreover,  I  do  not  believe  that  any 
ornithologist  would  in  this  case  place  the  English  carrier, 
the  short-faced  tumbler,  the  runt,  the  barb,  pouter,  and 
fantail  in  the  same  genus;  more  especially  as  in  each  of 
these  breeds  several  truly-inherited  sub-breeds,  or  species, 
as  he  would  call  them,  could  be  shown  him. 

Great  as  are  the  differences  between  the  breeds  of  the 
pigeon,  I  am  fully  convinced  that  the  common  opinion  of 
naturalists  is  correct,  namely,  that  all  jtre  descended  from 
the  rock-pigeon  (Columbia  livia),  mcl u din g u ncl er  this 
term  several  geographical  races  or  sub-species,  which  differ 
from  each  other  in  the  most  trifling  respects.  As  several 
of  the  reasons  which  have  led  me  to  this  belief  are  in  some 
degree  applicable  in  other  cases,  I  will  here  briefly  give 
them.  If  the  several  breeds  are  not  varieties,  and  have 
not  proceeded  from  the  rock-pigeon,  they  must  have  de¬ 
scended  from  at  least  seven  or  eight  aboriginal  stocks;  for 
it  is  impossible  to  make  the  present  domestic  breeds  by  the 
crossing  of  any  lesser  number;  how,  for  instance,  could 
a  pouter  be  produced  by  crossing  two  breeds  unless 
one  of  the  parent-stocks  possessed  the  characteristic 
enormous  crop?  The  supposed  aboriginal  stocks  must 
all  have  been  rock-pigeons,  that  is,  they  did  not  breed 
or  willingly  perch  on  trees.  But  besides  0.  livia,  with 
its  geographical  sub  species,  only  two  or  three  other 
species  of  rock-pigeons  are  known;  and  these  have  not  any 
of  the  characters  of  the  lomestic  breeds.  Hence  the  sup¬ 
posed  aboriginal  stocks  must  either  still  exist  in  the  coun¬ 
tries  where  they  were  originally  domesticated,  and  yet  be 
unknown  to  ornithologists;  and  this,  considering  their 
size,  habits  and  remarkable  characters,  seems  improbable; 
or  they  must  have  become  extinct  in  the  wild  state.  But 
birds  breeding  on  precipices,  and  good  flyers,  are  unlikely 


DOMESTIC  PIGEONS. 


21 


to  be  exterminated;  and  the  common  rock-pigeon,  which 
has  the  same  habits  with  the  domestic  breeds,  has  not  been 
exterminated  even  on  several  of  the  smaller  British  islets, 
or  on  the  shores  of  the  Mediterranean.  Hence  the  sup¬ 
posed  extermination  of  so  many  species  having  similar 
habits  with  the  rock-pigeon  seems  a  very  rash  assumption. 
Moreover,  the  several  above-named  domesticated  breeds 
have  been  transported  to  all  parts  of  the  world,  and,  there¬ 
fore,  some  of  them  must  have  been  carried  back  again  into 
their  native  country;  but  not  one  has  become  wild  or  feral, 
though  the  dovecot-pigeon,  which  is  the  rock-pigeon  in  a 
very  slightly  altered  state,  has  become  feral  in  several 
places.  Again,  all  recent  experience  shows  that  it  is  diffi¬ 
cult  to  get  wild  animals  to  breed  freely  under  domestica¬ 
tion;  yet  on  the  hypothesis  of  the  multiple  origin  of  our 
pigeons,  it  must  be  assumed  that  at  least  seven  or  eight 
species  were  so  thoroughly  domesticated  in  ancient  times 
by  half-civilized  man  as  to  be  quite  prolific  under  confine¬ 
ment. 

An  argument  of  great  weight,  and  applicable  in  several 
other  cases,  is,  that  the  above-specified  breeds,  though 
agreeing  generally  with  the  wild  rock-pigeon  in  constitu¬ 
tion,  habits,  voice,  coloring,  and  in  most  parts  of  their 
structure,  yet  are  certainly  highly  abnormal  in  other  parts; 
we  may  look  in  vain  through  the  whole  great  family  of  Col- 
umbidse  for  a  beak  like  that  of  the  English  carrier,  or  that 
of  the  short-faced  tumbler,  or  barb;  for  reversed  feathers 
like  those  of  the  Jacobin;  for  a  crop  like  that  of  the  pouter; 
for  tail-feathers  like  those  of  the  fantail.  Hence  it  must 
be  assumed,  not  only  that  half-civilized  man  succeeded  in 
thoroughly  domesticating  several  species,  but  that  he  in¬ 
tentionally  or  by  chance  picked  out  extraordinarily  abnor¬ 
mal  species;  and  further,  that  these  very  species  have  since 
all  become  extinct  or  unknown.  So  many  strange  contin¬ 
gencies  are  improbable  in  the  highest  degree. 

Some  facts  in  regard  to  the  coloring  of  pigeons  well  de¬ 
serve  consideration.  The  rock-pigeon  is  of  a  slaty-blue, 
with  white  loins;  but  the  Indian  sub-species,  0.  interme¬ 
dia  of  Strickland,  has  this  part  bluish.  The  tail  has  a  ter¬ 
minal  dark  bar,  with  the  outer  feathers  externally  edged  at 
the  base  with  white.  The  wings  have  two  black  bars. 
Some  semi-domestic  breeds,  and  some  truly  wild  breeds. 


22 


DOMESTIC  PIGEON’S. 


Lave,  besides  the  two  black  bars,  the  wings  checkered  with 
black.  *  These  several  marks  do  not  occur  together  in  any 
other  species  of  the  whole  family.  Now,  in  every  one  of  the 
domestic  breeds,  taking  thoroughly  well-bred  birds,  all  the 
above  marks,  even  to  the  white  edging  of  the  outer  tail- 
feathers,  sometimes  concur  perfectly  developed.  More¬ 
over,  when  birds  belonging  to  two  or  more  distinct  breeds 
are  crossed,  none  of  which  are  blue  or  have  any  of  the 
above-specified  marks,  the  mongrel  offspring  are  very 
apt  suddenly  to  acquire  these  characters.  To  give 
one  instance  out  of  several  which  I  have  observed : 
I  crossed  some  white  fantails,  which  breed  very 
true,  with  some  black  barbs — and  it  so  happens  that 
blue  varieties  of  barbs  are  so  rare  that  I  never  heard  of  an 
instance  in  England;  and  the  mongrels  were  black,  brown 
and  mottled.  I  also  crossed  a  barb  with  a  spot,  which  is  a 
white  bird  with  a  red  tail  and  red  spot  on  the  forehead, 
and  which  notoriously  breeds  very  true;  the  mongrels  were 
dusky  and  mottled.  I  then  crossed  one  of  the  mongrel 
barb-fantails  with  a  mongrel  barb-spot,  and  they  produced 
a  bird  of  as  beautiful  a  blue  color,  with  the  white  loins, 
double  black  wing-bar,  and  barred  and  white-edged  tail- 
feathers,  as  any  wild  rock-pigeon  !  We  can  understand 
these  facts,  on  the  well-known  principle  of  reversion  to 
ancestral  characters,  if  all  the  domestic  breeds  are  de¬ 
scended  from  the  rock-pigeon.  But,  if  we  deny  this,  we 
must  make  one  of  the  two  following  highly  improbable 
suppositions.  Either,  first,  that  all  the  several  imagined 
aboriginal  stocks  were  colored  and  marked  like  the  rock- 
pigeon,  although  no  other  existing  species  is  thus  colored 
and  marked,  so  that  in  each  separate  breed  there  might  be 
a  tendency  to  revert  to  the  very  same  colors  and  markings. 
Or,  secondly,  that  each  breed,  even  the  purest,  has  within 
a  dozen,  or  at  most  within  a  score,  of  generations,  been 
crossed  by  the  rock-pigeon:  I  say  within  a  dozen  or  twenty 
generations,  for  no  instance  is  known  of  crossed  descend¬ 
ants  reverting  to  an  ancestor  of  foreign  blood,  removed  by 
a  greater  number  of  generations.  In  a  breed  which  has 
been  crossed  only  once  the  tendency  to  revert  to  any 
character  derived  from  such  a  cross  will  naturally  become 
less  and  less,  as  in  each  succeeding  generation  there  will  be 
less  of  the  foreign  blood;  but  when  there  has  been  no  cross. 


DOMESTIC  PIGEONS. 


23 


and  there  is  a  tendency  in  the  breed  to  revert  to  a  character 
which  was  lost  during  some  former  generation,  this 
tendency,  for  all  that  we  can  see  to  the  contrary,  may  be 
transmitted  undiminished  for  an  indefinite  number  of  gen¬ 
erations.  These  two  distinct  cases  of  reversion  are  often 
confounded  together  by  those  who  have  written  on  in¬ 
heritance. 

Lastly,  the  hybrids  or  mongrels  from  between  all  the 
breeds  of  the  pigeon  are  perfectly  fertile,  as  I  can  state 
from  my  own  observations,  purposely  made,  on  the  most 
distinct  breeds.  Now,  hardly  any  cases  have  been  ascer¬ 
tained  with  certainty  of  hybrids  from  two  quite  distinct 
species  of  animals  being  perfectly  fertile.  Some  authors 
believe  that  long-continued  domestication  eliminates  this 
strong  tendency  to  sterility  in  species.  From  the  history 
of  the  dog,  and  of  some  other  domestic  animals,  this  con¬ 
clusion  is  probably  quite  correct,  if  applied  to  species 
closely  related  to  each  other.  But  to  extend  it  so  far  as  to 
suppose  that  species,  aboriginally  as  distinct  as  carriers, 
tumblers,  pouters,  and  fantails  now  are,  should  yield  off¬ 
spring  perfectly  fertile  inter  se,  would  be  rash  in  the 
extreme. 

From  these  several  reasons,  namely,  the  improbability 
of  man  having  formerly  made  seven  or  eight  supposed 
species  of  pigeons  to  breed  freely  under  domestication — • 
these  supposed  species  being  quite  unknown  in  a  wild  state, 
and  their  not  having  become  anywhere  feral — these  species 
presenting  certain  very  abnormal  characters,  as  compared 
with  all  other  Columbidae,  though  so  like  the  rock-pigeon 
in  most  respects — the  occasional  reappearance  of  the  blue 
color  and  various  black  marks  in  all  the  breeds,  both  when 
kept  pure  and  when  crossed — and  lastly,  the  mongrel  off¬ 
spring  being  perfectly  fertile — from  these  several  reasons, 
taken  together,  we  may  safely  conclude  that  all  our 
domestic  breeds  are  descended  from  the  rock-pigeon  or 
Columbae  livia  with  its  geographical  sub-species. 

In  favor  of  this  view,  I  may  add,  firstly,  that  the  wild 
C.  livia  has  been  found  capable  of  domestication  in  Europe 
and  in  India;  and  that  it  agrees  in  habits  and  in  a  great 
number  of  points  of  structure  with  all  the  domestic  breeds. 
Secondly,  that  although  an  English  carrier  or  a  short¬ 
faced  tumbler  differs  immensely  in  certain  characters  from 


u 


DOMESTIC  PIGEONS, . 


the  rock-pigeon,  yet  that  by  comparing  the  several  sub¬ 
breeds  of  these  two  races,  more  especially  those  brought 
from  distant  countries,  we  can  make,  between  them  and 
the  rocL-pigeon,  an  almost  perfect  series;  so  we  can  in 
some  other  cases,  but  not  with  all  the  breeds.  Thirdly, 
those  characters  which  are  mainly  distinctive  of  each  breed 
are  in  each  eminently  variable,  for  instance,  the  wattle  and 
length  of  beak  of  the  carrier,  the  shortness  of  that  of  the 
tumbler,  and  the  number  of  tail-feathers  in  the  fantail; 
and  the  explanation  of  this  fact  will  be  obvious  when  we 
treat  of  selection.  Fourthly,  pigeons  have  been  watched 
and  tended  with  the  utmost  care  and  loved  by  many 
people.  They  have  been  domesticated  for  thousands  of 
years  in  several  quarters  of  the  world;  the  earliest  known 
record  of  pigeons  is  in  the  fifth  ^Egyptian  dynasty,  about 
3000  B.c.,  as  was  pointed  out  to  me  by  Professor  Lepsius; 
but  Mr.  Birch  informs  me  that  pigeons  are  given  in  a  bill 
of  fare  in  the  previous  dynasty.  In  the  time  of  the 
Romans,  as  we  hear  from  Pliny,  immense  prices  were  given 
for  pigeons;  “nay,  they  are  come  to  this  pass,  that  they 
can  reckon  up  their  pedigree  and  race.”  Pigeons  were 
much  valued  by  Akber  Khan,  in  India,  about  the  year 
1600;  never  less  than  20,000  pigeons  were  taken  with  the 
court.  “  The  monarchs  of  Iran  and  Turan  sent  him  some 
very  rare  birds;”  and,  continues  the  courtly  historian, 
“His  Majesty,  by  crossing  the  breeds,  which  method  was 
never  practiced  before,  has  improved  them  astonishingly.” 
About  this  same  period  the  Dutch  were  as  eager  about 
pigeons  as  were  the  old  Romans.  The  paramount  impor¬ 
tance  of  these  considerations  in  explaining  the  immense 
amount  of  variation  which  pigeons  have  undergone,  will 
likewise  be  obvious  when  we  treat  of  selection.  We  shall 
then,  also,  sec  how  it  is  that  the  several  breeds  so  often 
have  a  somewha  .  monstrous  character.  It  is  also  a  most 
favorable  circumstance  for  the  production  of  distinct 
breeds,  hat  male  and  female  pigeons  can  be  easily  mated 
for  life;  and  thus  different  breeds  can  be  kept  together  in 
the  same  aviary. 

I  have  discussed  the  probable  origin  of  domestic  pigeons 
at  some,  yet  quite  insufficient,  length;  because  when  I  first 
kept  pigeons  and  watched  the  several  kinds,  well  knowing 
haw  truly  they  breed,  ^  foit  fully  as  much  difficulty  in 


SELECTION  BY  MAN. 


25 


believing  that  since  they  had  been  domesticated  they  had 
all  proceeded  from  a  common  parent,  as  any  naturalist 
could  in  coming  to  a  similar  conclusion  in  regard  to  the 
many  species  of  finches,  or  other  groups  of  birds,  in 
nature.  One  circumstance  has  struck  me  much;  namely, 
that  nearly  all  the  breeders  of  the  various  domestic 
animals  and  the  cultivators  of  plants,  with  whom  I 
have  conversed,  or  whose  treatises  I  have  read,  are 
firmly  convinced  that  the  several  breeds  to  which  each 
has  attended,  are  descended  from  so  many  aboriginally  dis¬ 
tinct  species.  Ask,  as  I  have  asked,  a  celebrated  raiser  of 
Hereford  cattle,  whether  his  cattle  might  not  have  de¬ 
scended  from  Long-horns,  or  both  from  a  common  parent- 
stock,  and  he  will  laugh  you  to  scorn.  I  have  never  met  a 
pigeon,  or  poultry,  or  duck,  or  rabbit  fancier,  who  was  not 
fully  convinced  that  each  main  breed  was  descended  from  a 
distinct  species.  Van  Mons,  in  his  treatise  on  pears  and 
applet,  shows  how  utterly  he  disbelieves  that  the  several 
sorts,  for  instance  a  Ribston-pippin  or  Codlin-apple,  could 
ever  have  proceeded  from  the  seeds  of  the  same  tree.  In¬ 
numerable  other  examples  could  be  given.  The  explana¬ 
tion,  I  think,  is  simple:  from  long- continued  study  they 
are  strongly  impressed  with  the  differences  between  the 
several  races;  and  though  they  well  know  that  each  race 
varies  slightly,  for  they  win  their  prizes  by  selecting  such 
slight  differences,  yet  they  ignore  all  general  arguments, 
and  refuse  to  sum  up  in  their  minds  slight  differences 
accumulated  during  many  successive  generations.  May 
not  those  naturalists  who,  knowing  far  less  of  the 
laws  of  inheritance  than  does  the  breeder,  and  know¬ 
ing  no  more  than  he  does  of  the  intermediate  links  in  the 
long  lines  of  descent,  yet  admit  that  many  of  our  domestic 
races  are  descended  from  the  same  parents — may  they  not 
learn  a  lesson  of  caution,  when  they  deride  the  idea  of 
species  in  a  state  of  nature  being  lineal  descendants  of  other 
species? 

PRINCIPLES  OF  SELECTION  ANCIENTLY  FOLLOWED,  AND 

THEIR  EFFECTS. 

Let  ns  now  briefly  consider  the  steps  by  which  domestic 
races  have  been  produced,  either  from  one  or  from  several 


26 


SELECTION  BY  MAN 


allied  species.  Some  effect  may  be  attributed  to  the  direct 
and  definite  action  of  the  external  conditions  of  life,  and 
some  to  habit;  but  he  would  be  a  bold  man  who  would  ac¬ 
count  by  such  agencies  for  the  differences  between  a  dray 
and  race-horse,  a  greyhound  and  bloodhound,  a  carrier  and 
tumbler  pigeon.  One  of  the  most  remarkable  features  in 
our  domesticated  races  is  that  we  see  in  them  adaptation, 
not  indeed  to  the  animal's  or  plant's  own  good,  but  to 
man’s  use  or  fancy.  Some  variations  useful  to  him  have 
probably  arisen  suddenly,  or  by  one  step;  many  botanists, 
for  instance,  believe  that  the  fuller’s  teasel,  with  its  hooks, 
which  can  not  be  rivaled  by  any  mechanical  contrivance, 
is  only  a  variety  of  the  wild  Dipsacus;  and  this  amount  of 
change  may  have  suddenly  arisen  in  a  seedling.  So  it  has 
probably  been  with  the  turnspit  dog;  and  this  is  known  to 
have  been  the  case  with  the  ancon  sheep.  But  when  we 
compare  the  dray-horse  and  race-horse,  the  dromedary  and 
camel,  the  various  breeds  of  sheep  fitted  either  for  culti¬ 
vated  land  or  mountain  pasture,  with  the  wool  of  one 
breed  good  for  one  purpose,  and  that  of  another  breed  for 
another  purpose;  when  we  compare  the  many  breeds  of 
dogs,  each  good  for  man  in  different  ways;  when  we  com¬ 
pare  the  game-cock,  so  pertinacious  in  battle,  with  other 
breeds  so  little  quarrelsome,  with  “  everlasting  layers " 
which  never  desire  to  sit,  and  with  the  bantam  so  small  and 
elegant;  when  we  compare  the  host  of  agricultural,  culi¬ 
nary,  orchard  and  flower-garden  races  of  plants,  most  useful 
to  man  at  different  seasons  and  for  different  purposes,  or  so 
beautiful  in  his  eyes,  we  must,  I  think,  look  further  than 
to  mere  variability.  We  can  not  suppose  that  all  the 
breeds  were  suddenly  produced  as  perfect  and  as  useful  as 
we  now  see  them;  indeed,  in  many  cases,  we  know  that 
this  has  not  been  their  histoiy.  The  key  is  man's  power  of 
accumulative  selection:  nature  gives  successive  variations; 
man  adds  them  up  in  certain  directions  useful  to  him.  In 
this  sense  he  may  be  said  to  have  made  for  himself  useful 
breeds. 

The  great  power  of  this  principle  of  selection  is  not 
hypothetical.  It  is  certain  that  several  of  our  eminent 
breeders  have,  even  within  a  single  lifetime,  modified  to  a 
large  extent  their  breeds  of  cattle  and  sheep.  In  order 
fully  to  realize  what  they  have  done  it  is  almost  necessary 


SELECTION  BT  MAN. 


27. 


to  read  several  of  the  many  treatises  devoted  to  this  sub¬ 
ject,  and  to  inspect  the  animals.  Breeders  habitually 
speak  of  an  animal's  organization  as  something  plastic, 
which  they  can  model  almost  as  they  please.  If  I  had 
'  space  I  could  quote  numerous  passages  to  this  effect  from 
highly  competent  authorities.  Youatt,  who  was  probably 
better  acquainted  with  the  works  of  agriculturists  than 
almost  any  other  individual,  and  who  was  himself  a  very 
good  judge  of  animals,  speaks  of  the  principle  of  selection 
as  “that  which  enables  the  agriculturist,  not  only  to 
modify  the  character  of  his  flock,  but  to  change  it 
altogether.  It  is  the  magician's  wand,  by  means  of  which 
he  may  summon  into  life  whatever  form  and  mold  he 
pleases."  Lord  Somerville,  speaking  of  what  breeders 
have  done  for  sheep,  says:  “It  would  seem  as  if  they  had 
chalked  out  upon  a  wall  a  form  perfect  in  itself,  and  then 
had  given  it  existence."  In  Saxony  the  importance  of  the 
principle  of  selection  in  regard  to  merino  sheep  is  so  fully 
recognized  that  men  follow  it  as  a  trade:  the  sheep  are 
placed  on  a  table  and  are  studied,  like  a  picture  by  a  con¬ 
noisseur;  this  is  done  three  times  at  intervals  of  months, 
and  the  sheep  are  each  time  marked  and  classed,  so  that 
the  very  best  may  ultimately  be  selected  for  breeding. 

What  English  breeders  have  actually  effected  is  proved 
by  the  enormous  prices  given  for  animals  with  a  good  ped¬ 
igree;  and  these  have  been  exported  to  almost  every 
quarter  of  the  world.  The  improvement  is  by  no  means 
generally  due  to  crossing  different  breeds;  all  the  best 
breeders  are  strongly  opposed  to  this  practice,  except  some¬ 
times  among  closely  allied  sub-breeds.  And  when  a  cross 
has  been  made,  the  closest  selection  is  far  more  indispen¬ 
sable  even  than  in  ordinary  cases.  If  selection  consisted 
merely  in  separating  some  very  distinct  variety  and  breed¬ 
ing  from  it,  the  principle  would  be  so  obvious  as  hardly  to 
be  worth  notice;  but  its  importance  consists  in  the  great 
effect  produced  by  the  accumulation  in  one  direction, 
during  successive  generations,  of  differences  absolutely 
inappreciable  by  an  uneducated  eye — differences  which  I 
for  one  have  vainly  attempted  to  appreciate.  Not  one  man 
in  a  thousand  has  accuracy  of  eye  and  judgment  sufficient 
to  become  an  eminent  breeder.  If  gifted  with  these  qual¬ 
ities,  and  he  studies  his  subject  for  years,  and  devotes  his 


28 


SELECTION  BY  MAN. 


lifetime  to  it  with  indomitable  perseverance,  he  will  suc¬ 
ceed,  and  may  make  great  improvements;  if  he  wants  any 
of  these  qualities,  he  will  assuredly  fail.  Few  would  read- 
ily  believe  in  the  natural  capacity  and  years  of  practice 
requisite  to  become  even  a  skillful  pigeon-fancier. 

The  same  principles  are  followed  by  horticulturists;  but 
the  variations  are  here  often  more  abrupt.  ~No  one  sup¬ 
poses  that  our  choicest  productions  have  been  produced  by 
a  single  variation  from  the  aboriginal  stock.  We  have 
proofs  that  this  has  not  been  so  in  several  cases  in  which 
exact  records  have  been  kept;  thus,  to  give  a  very  trifling 
instance,  the  steadily  increasing  size  of  the  common  goose¬ 
berry  may  be  quoted.  We  see  an  astonishing  improvement 
in  many  florists’  flowers,  when  the  flowers  of  the  present 
day  are  compared  with  drawings  made  only  twenty  or 
thirty  years  ago.  When  a  race  of  plants  is  once  pretty  well 
established,  the  seed-raisers  do  not  pick  out  the  best  plants, 
but  merely  go  over  their  seed-beds,  and  pull  up  the 
“  rogues,”  as  they  call  the  plants  that  deviate  from  the 
proper  standard.  With  animals  this  kind  of  selection  is, 
in  fact,  likewise  followed;  for  hardly  any  one  is  so  careless 
as  to  breed  from  his  worst  animals. 

In  regard  to  plants,  there  is  another  means  of  observing 
the  accumulated  effects  of  selection — namely,  by  comparing 
the  diversity  of  flowers  in  the  different  varieties  of  the  same 
species  in  the  flower-garden;  the  diversity  of  leaves,  pods, 
or  tubers,  or  whatever  part  is  valued,  in  the  kitchen-garden, 
in  comparison  with  the  flowers  of  the  same  varieties;  and 
the  diversity  of  fruit  of  the  same  species  in  the  orchard,  in 
comparison  with  the  leaves  and  flowers  of  the  same  set  of 
varieties.  See  how  different  the  leaves  of  the  cabbage  are, 
and  how  extremely  alike  the  flowers;  how  unlike  the  flow¬ 
ers  of  the  heartsease  are,  and  how  alike  the  leaves;  how 
much  the  fruit  of  the  different  kinds  of  gooseberries  differ 
in  size,  color,  shape  and  hairyness,  and  yet  the  flowers  pre¬ 
sent  very  slight  differences.  It  is  not  that  the  varieties 
which  differ  largely  in  some  one  point  do  not  differ  at  all 
in  other  points;  this  is  hardly  ever — I  speak  after  careful 
observation — perhaps  never,  the  case.  The  law  of  corre¬ 
lated  variation,  the  importance  of  which  should  never  be 
overlooked,  will  insure  some  dif  erences;  but,  as  a  general 
rule,  it  cannot  be  doubted  that  the  continued  selection  of 


UNCONSCIOUS  SELECTION. 


29 


slight  variations,  either  in  the  leaves,  the  flowers,  or  the 
fruit,  will  produce  races  differing  from  each  other  chiefly 
in  these  characters. 

It  may  be  objected  that  the  principle  of  selection  has 
been  reduced  to  methodical  practice  for  scarcely  more  than 
three-quarters  of  a  century;  it  has  certainly  been  more  at¬ 
tended  to  of  late  years,  and  many  treatises  have  been  pub¬ 
lished  on  the  subject;  and  the  result  has  been,  in  a  corre¬ 
sponding  degree,  rapid  and  important.  But  it  is  very  far 
from  true  that  the  principle  is  a  modern  discovery.  I  could 
give  several  references  to  works  of  high  antiquity,  in  which 
the  full  importance  of  the  principle  is  acknowledged.  In 
rude  and  barbarous  periods  of  English  history  choice  ani¬ 
mals  were  often  imported,  and  laws  were  passed  to  prevent 
their  exportation:  the  destruction  of  horses  under  a  certain 
size  was  ordered,  and  this  may  be  compared  to  the 
“  roguing "  of  plants  by  nurserymen.  The  principle  of 
selection  I  find  distinctly  given  in  an  ancient  Chinese  ency¬ 
clopedia.  Explicit  rules  are  laid  down  by  some  of  the 
Koman  classical  writers.  From  passages  in  Genesis,  it  is 
clear  that  the  color  of  domestic  animals  was  at  that  early 
period  attended  to.  Savages  now  sometimes  cross  their 
dogs  with  wild  canine  animals,  to  improve  the  breed,  and 
they  formerly  did  so,  as  is  attested  by  passages  in  Pliny. 
The  savages  in  South  Africa  match  their  draft  cattle  by 
color,  as  do  some  of  the  Esquimaux  their  team  of  dogs. 
Livingstone  states  that  good  domestic  breeds  are  highly 
valued  by  the  negroes  in  the  interior  of  Africa  who  have 
not  associated  with  Europeans.  Some  of  these  facts  do 
not  show  actual  selection,  but  they  show  that  the  breeding 
of  domestic  animals  was  carefully  attended  to  in  ancient 
times,  and  is  now  attended  to  by  the  lowest  savages.  It 
would,  indeed,  have  been  a  strange  fact,  had  attention  not 
been  paid  to  breeding,  for  the  inheritance  of  good  and  bad 
qualities  is  so  obvious. 

UNCONSCIOUS  SELECTION. 

At  the  present  time,  eminent  breeders  try  by  methodical 
selection,  with  a  distinct  object  in  view,  to  make  a  new 
strain  or  sub-breed,  superior  to  anything  of  the  kind  in  the 
country.  But,  for  our  purpose,  a  form  of  selection,  which 
may  be  called  unconscious,  and  which  results  from  every 


30 


UNCONSCIOUS  SELECTION. 


one  trying  to  possess  and  breed  from  the  best  individual 
animals,  is  more  important.  Thus,  a  man  who  intends 
keeping  pointers  naturally  tries  to  get  as  good  dogs  as  he  can, 
and  afterward  breeds  from  his  own  best  dogs,  but  he  has 
no  wish  or  expectation  of  permanently  altering  the  breed. 
Nevertheless  we  may  infer  that  this  process,  continued 
during  centuries,  would  improve  and  modify  any  breed,  in 
the  same  way  as  Bakewell,  Collins,  etc.,  by  this  very  same 
process,  only  carried  on  more  methodically,  did  greatly 
modify,  even  during  their  lifetimes,  the  forms  and  qualities 
of  their  cattle.  Slow  and  insensible  changes  of  this  kind 
can  never  be  recognized  unless  actual  measurements  or  care¬ 
ful  drawings  of  the  breeds  in  question  have  been  made  long 
ago,  which  may  serve  for  comparison.  In  some  cases,  how¬ 
ever,  unchanged,  or  but  little  changed,  individuals  of  the 
same  breed  exist  in  less  civilized  districts,  where  the  breed 
has  been  less  improved.  There  is  reason  to  believe  that 
King  Charles5  spaniel  has  been  unconsciously  modified  to  a 
large  extent  since  the  time  of  that  monarch.  Some  highly 
competent  authorities  are  convinced  that  the  setter  is 
directly  derived  from  the  spaniel,  and  has  probably  been 
slowly  altered  from  it.  It  is  known  that  the  English 
pointer  has  been  greatly  changed  within  the  last  century, 
and  in  this  case  the  change  has,  it  is  believed,  been  chiefly 
effected  by  crosses  with  the  foxhound;  but  what  concerns 
us  is,  that  the  change  has  been  effected  unconsciously  and 
gradually,  and  yet  so  effectually  that,  though  the  old 
Spanish  pointer  certainly  came  from  Spain,  Mr.  Borrow 
has  not  seen,  as  I  am  informed  by  him,  any  native  dog  in 
Spain  like  our  pointer. 

By  a  similar  process  of  selection,  and  by  careful  training, 
English  race-horses  have  come  to  surpass  in  fleetness  and  size 
the  parent  Arabs,  so  that  the  latter,  by  the  regulations  for 
the  Goodwood  Races,  are  favored  in  the  weights  which  they 
carry.  Lord  Spencer-  and  others  have  shown  how  the 
cattle  of  England  have  increased  in  weight  and  in  early 
maturity,  compared  with  the  stock  formerly  kept  in  this 
country.  By  comparing  the  accounts  given  in  various  old 
treatises  of  the  former  and  present  state  of  carrier  and 
tumbler  pigeons  in  Britain,  India  and  Persia,  we  can  trace 
the  stages  through  which  they  have  insensibly  passed,  and 
come  to  differ  so  greatly  from  the  rock-pigeon. 


UNCONSCIOUS  SELECTION. 


31 


Youatt  gives  an  excellent  illustration  of  the  effects  of  a 
course  of  selection  which  may  be  considered  as  unconscious, 
in  so  far  that  the  breeders  could  never  have  expected,  or 
even  wished,  to  produce  the  result  which  ensued — namely, 
the  production  of  the  distinct  strains.  The  two  flocks  of 
Leicester  sheep  kept  by  Mr.  Buckley  and  Mr.  Burgess,  as 
Mr.  Youatt  remarks,  “  Have  been  purely  bred  from  the 
original  stock  of  Mr.  Bakewell  for  upward  of  fifty  years. 
There  is  not  a  suspicion  existing  in  the  mind  of  any  one  at 
all  acquainted  with  the  subject  that  the  owner  of  either  of 
them  has  deviated  in  any  one  instance  from  the  pure  blood 
of  Mr.  Bake  well’s  flock,  and  yet  the  difference  between  the 
sheep  possessed  by  these  two  gentlemen  is  so  great  that 
they  have  the  appearance  of  being  quite  different  varieties.” 

If  there  exist  savages  so  barbarous  as  never  to  think  of 
the  inherited  character  of  the  offspring  of  their  domestic 
animals,  yet  any  one  animal  particularly  useful  to  them, 
for  any  special  purpose,  would  be  carefully  preserved 
during  famines  and  other  accidents,  to  which  savages  are 
so  liable,  and  such  choice  animals  would  thus  generally 
leave  more  offspring  than  the  inferior  ones;  so  that  in  this 
case  there  would  be  a  kind  of  unconscious  selection  going 
on.  We  see  the  value  set  on  animals  even  by  the  bar- 1 
barians  of  Tierra  del  Fuego,  by  their  killing  and  devouring  l 
their  old  women,  in  times  of  dearth,  as  of  less  value  than  * 
their  dogs. 

In  plants  the  same  gradual  process  of  improvement 
through  the  occasional  preservation  of  the  best  individuals, 
whether  or  not  sufficiently  distinct  to  be  ranked  at  their 
first  appearance  as  distinct  varieties,  and  whether  or  not 
two  or  more  species  or  races  have  become  blended  together 
by  crossing,  may  plainly  be  recognized  in  the  increased  size 
and  beauty  which  we  now  see  in  the  varieties  of  the  hearts¬ 
ease,  rose,  pelargonium,  dahlia  and  other  plants,  when 
compared  with  the  older  varieties  or  wdth  their  parent- 
stocks.  Ho  one  would  ever  expect  to  get  a  first-rate  hearts¬ 
ease  or  dahlia  from  the  seed  of  a  wild  plant.  No  one 
would  expect  to  raise  a  first-rate  melting  pear  from  the 
seed  of  the  wild  pear,  though  he  might  succeed  from  a 
poor  seedling  growing  wild,  if  it  had  come  from  a  garden- 
stock.  The  pear,  though  cultivated  in  classical  times, 
appears,  from  Pliny’s  description,  to  have  been  a  fruit  of 


32 


UNCONSCIOUS  SELECTION. 


very  inferior  quality.  I  have  seen  great  surprise  expressed 
in  horticultural  works  at  the  wonderful  skill  of  gardeners 
in  having  produced  such  splendid  results  from  such  poor 
materials;  but  the  art  has  been  simple,  and,  as  far  as  the 
final  result  is  concerned,  has  been  followed  almost  uncon¬ 
sciously.  It  lias  consisted  in  always  cultivating  the  best 
known  variety,  sowing  its  seeds,  and,  when  a  slightly  better 
variety  chanced  to  appear,  selecting  it,  and  so  onward. 
But  the  gardeners  of  the  classical  period,  who  cultivated 
the  best  pears  which  they  could  procure,  never  thought* 
what  splendid  fruit  we  should  eat;  though  we  owe  our 
excellent  fruit  in  some  small  degree  to  their  having  naturally 
chosen  and  preserved  the  best  varieties  they  could  any¬ 
where  find. 

A  large  amount  of  change,  thus  slowly  and  uncon¬ 
sciously  accumulated,  explains,  as  I  believe,  the  well- 
known  fact,  that  in  a  number  of  cases  we  cannot 
recognize,  and  therefore  do  not  know,  the  wild  parent- 
stocks  of  the  plants  which  have  been  longest  cultivated 
in  our  flower  and  kitchen  gardens.  It  it  has  taken 
centuries  or  thousands  of  years  to  improve  or  modify  most 
of  our  plants  up  to  their  present  standard  of  usefulness  to 
man,  we  can  understand  liow  it  is  that  neither  Australia, 
the  Cape  of  Good  Hope,  nor  any  other  region  inhabited  by 
quite  uncivilized  man,  has  afforded  us  a  single  plant  worth 
culture.  It  is  not  that  these  countries,  so  rich  in  species, 
do  not  by  a  strange  chance  possess  the  aboriginal  stocks  of 
any  useful  plants,  but  that  the  native  plants  have  not  been 
improved  by  continued  selection  up  to  a  standard  of  per¬ 
fection  comparable  with  that  acquired  by  the  plants  in 
countries  anciently  civilized. 

In  regard  to  the  domestic  animals  kept  by  uncivilized 
man,  it  should  not  be  overlooked  that  they  almost  always 
have  to  struggle  for  their  own  food,  at  least  during  certain 
seasons.  And  in  two  countries  very  differently  circum¬ 
stanced,  individuals  of  the  same  species,  having  slightly 
different  constitutions  or  structure,  would  often  suc¬ 
ceed  better  in  the  one  country  than  in  the  other; 
and  thus  by  a  process  of  “natural  selection,”  as 
will  hereafter  be  more  fully  explained,  two  sub¬ 
breeds  might  be  formed.  This,  perhaps,  partly 
explains  why  the  varieties  kept  by  savages,  as  has  been 


UNCONSCIOUS  SELECTION. 


33 


remarked  by  some  authors,  have  more  of  the  character  of 
true  species  than  the  varieties  kept  in  civilized  countries. 

On  the  view  here  given  of  the  important  part  which 
selection  by  man  has  played,  it  becomes  at  once  obvious, 
how  it  is  that  our  domestic  races  show  adaptation  in  their 
structure  or  in  their  habits  to  man's  wants  or  fancies.  We 
can,  I  think,  further  understand  the  frequently  abnormal 
character  of  our  domestic  races,  and  likewise  their  differ¬ 
ences  being  so  great  in  external  characters,  and  relatively 
so  slight  in  internal  parts  or  organs.  Man  can  hardly 
select,  or  only  with  much  difficulty,  any  deviation  of 
structure  excepting  such  as  is  externally  visible;  and 
indeed  he  rarely  cares  for  what  is  internal.  He  can  never 
act  by  selection,  excepting  on  variations  which  are  first 
given  to  him  in  some  slight  degree  by  nature.  No  man 
would  ever  try  to  make  a  fantail  till  he  saw  a  pigeon  with 
a  tail  developed  in  some  slight  degree  in  an  unusual 
manner,  or  a  pouter  till  he  saw  a  pigeon  with  a  crop  of 
somewhat  unusual  size;  and  the  more  abnormal  or  unusual 
any  character  was  when  it  first  appeared,  the  more  likely 
it  would  be  to  catch  his  attention.  But  to  use  such  an  ex¬ 
pression  as  trying  to  make  a  fantail  is,  I  have  no  doubt,  in 
most  cases,  utterly  incorrect.  The  man  who  first  selected 
a  pigeon  with  a  slightly  larger  tail,  never  dreamed  what  the 
descendants  of  that  pigeon  would  become  through  long- 
continued,  partly  unconscious  and  partly  methodical,  selec¬ 
tion.  Perhaps  the  parent-bird  of  all  fantails  had  only 
fourteen  tail-feathers  somewhat  expanded,  like  the  present 
Java  fantail,  or  like  individuals  of  other  and  distinct 
breeds,  in  which  as  many  as  seventeen  tail-feathers  have 
been  counted.  Perhaps  the  first  pouter  pigeon  did  not  in¬ 
flate  its  crop  much  more  than  the  turbit  now  does 
the  upper  part  of  its  esophagus — a  habit  which  is  disre¬ 
garded  by  all  fanciers,  as  it  is  not  one  of  the  points  of  the 
breed. 

Nor  let  it  be  thought  that  some  great  deviation  of  struc¬ 
ture  would  be  necessary  to  catch  the  fancier’s  eye:  he  per¬ 
ceives  extremely  small  differences,  and  it  is  in  human 
nature  to  value  any  novelty,  however  slight,  in 
one’s  own  possession.  Nor  must  the  value  which  would 
formerly  have  been  set  on  any  slight  differences  in  the 
individuals  of  the  same  species,  be  judged  of  by  the  value 


34  CIRCUMSTANCES  FA  VORABLE  TO  SELECTION. 


which  is  now  set  on  them,  after  several  breeds  have  fairly 
been  established.  It  is  known  that  with  pigeons  many 
slight  variations  now  occasionally  appear,  but  these  are  re* 
jected  as  faults  or  deviations  from  the  standard  of  per¬ 
fection  in  each  breed.  The  common  goose  has  not  given 
rise  to  any  marked  varieties;  hence  the  Toulouse  and  the 
common  breed,  which  differ  only  in  color,  that  most  fleet¬ 
ing  of  characters,  have  lately  been  exhibited  as  distinct  at 
our  poultry  shows. 

These  views  appear  to  explain  what  has  sometimes  been 
noticed,  namely,  that  we  know  hardly  anything  about  the 
origin  or  history  of  any  of  our  domestic  breeds.  But,  in 
fact,  a  breed,  like  a  dialect  of  a  language,  can  hardly  be 
said  to  have  a  distinct  origin.  A  man  preserves  and  breeds 
from  an  individual  with  some  slight  deviation  of  structure, 
or  takes  more  care  than  usual  in  matching  his  best  animals, 
and  thus  improves  them,  and  the  improved  animals  slowly 
spread  in  the  immediate  neighborhood.  But  they  will  as 
yet  hardly  have  a  distinct  name,  and  from  being  only 
slightly  valued,  their  history  will  have  been  disregarded. 
When  further  improved  by  the  same  slow  and  gradual 
process,  they  will  spread  more  widely,  and  will  be  recog¬ 
nized  as  something  distinct  and  valuable,  and  will  then 
probably  first  receive  a  provincial  name.  In  semi-civilized 
countries,  with  little  free  communication,  the  spreading  of 
a  new  sub-breed  would  be  a  slow  process.  As  soon  as  the 
points  of  value  are  once  acknowledged,  the  principle,  as  I 
have  called  it,  of  unconscious  selection  will  always  tend — 
perhaps  more  at  one  period  than  at  another,  as  the  breed 
rises  or  falls  in  fashion — perhaps  more  in  one  district  than 
in  another,  according  to  the  state  of  civilization  of  the  in¬ 
habitants — slowly  to  add  to  the  characteristic  features  of 
the  breed,  whatever  they  may  be.  But  the  chance  will  bo 
infinitely  small  of  any  record  having  been  preserved  of  such 
slow,  varying  and  insensible  changes. 

CIRCUMSTANCES  FAVORABLE  TO  MAN’S  POWER  OF  SELEC¬ 
TION. 

I  will  now  say  a  few  words  on  the  circumstances,  favor¬ 
able  or  the  reverse,  to  man’s  power  of  selection.  A  high 
degree  of  variability  is  obviously  favorable,  as  freely  giving 


CIRCUMSTANCES  FAVORABLE  TO  SELECTION.  35 


the  materials  for  selection  to  work  on;  not  that  mere  in¬ 
dividual  differences  are  not  amply  sufficient,  with  extreme 
care,  to  allow  of  the  accumulation  of  a  large  amount  of 
modification  in  almost  any  desired  direction.  But  as 
variations  manifestly  useful  or  pleasing  to  man  appear  only 
occasionally,  the  chance  of  their  appearance  will  be  much 
increased  by  a  large  number  of  individuals  being  kept. 
Hence,  number  is  of  the  highest  importance  for  success. 
On  this  principle  Marshall  formerly  remarked,  with  respect 
to  the  sheep  of  part  of  Yorkshire,  “As  they  generally 
belong  to  poor  people,  and  are  mostly  in  small  lots ,  they 
never  can  be  improved.”  On  the  other  hand,  nurserymen, 
from  keeping  large  stocks  of  the  same  plant,  are  generally 
far  more  successful  than  amateurs  in  raising  new  and 
valuable  varieties.  A  large  number  of  individuals  of  an 
animal  or  plant  can  be  reared  only  where  the  conditions  for  its 
propagation  are  favorable.  When  the  individuals  are  scanty 
all  will  be  allowed  to  breed,  whatever  their  quality  may  be, 
and  this  will  effectually  prevent  selection.  But  probably  the 
most  important  element  is  that  the  animal  or  plant  should 
be  so  highly  valued  by  man,  that  the  closest  attention  is 
paid  to  even  the  slightest  deviations  in  its  qualities  or 
structure.  Unless  such  attention  be  paid  nothing  can  be 
effected.  I  have  seen  it  gravely  remarked,  that  it  was 
most  fortunate  that  the  strawberry  began  to  vary  just  when 
gardeners  began  to  attend  to  this  plant.  Ho  doubt  the 
strawberry  had  always  varied  since  it  was  cultivated,  but 
the  slight  varieties  had  been  neglected.  As  soon,  however, 
as  gardeners  picked  out  individual  plants  with  slightly 
larger,  earlier  or  better  fruit,  and  raised  seedlings  from 
them,  and  again  picked  out  the  best  seedlings  and  bred 
from  them,  then  (with  some  aid  by  crossing  distinct  species) 
those  many  admirable  varieties  of  the  strawberry  were 
raised  which  have  appeared  during  the  last  half-century. 

With  animals,  facility  in  preventing  crosses  is  an  im¬ 
portant  element  in  the  formation  of  new  races — at  least, 
in  a  country  which  is  already  stocked  with  other  races.  In 
this  respect  inclosure  of  the  land  plays  a  part.  Wander¬ 
ing  savages  or  the  inhabitants  of  open  plains  rarely  possess 
more  than  one  breed  of  the  same  species.  Pigeons  can  be 
mated  for  life,  and  this  is  a  great  convenience  to  the  fancier, 
for  thus  many  races  may  be  improved  and  kept  true. 


36  CIRCUMSTANCES  FA  VORABLE  TO  SELECTION. 


though  mingled  in  the  same  aviary;  and  this  circumstance 
must  have  largely  favored  the  formation  of  new  breeds. 
Pigeons,  I  may  add,  can  be  propagated  in  great  numbers 
and  at  a  very  quick  rate,  and  inferior  birds  may  be  freely 
rejected,  as  when  killed  they  serve  for  food.  On  the  other 
hand,  cats,  from  their  noctnral  rambling  habits,  can  not 
be  easily  matched,  and,  although  so  much  valued  by 
women  and  children,  we  rarely  see  a  distinct  breed  long 
kept  up;  such  breeds  as  we  do  sometimes  see  are  almost 
always  imported  from  some  other  country.  Although  I 
do  not  doubt  that  some  domestic  animals  vary  less  than 
others,  yet  the  rarity  or  absence  of  distinct  breeds  of  the 
cat,  the  donkey,  peacock,  goose,  etc.,  may  be  attributed  in 
main  part  to  selection  not  having  been  brought  into  play: 
in  cats,  from  the  difficulty  in  pairing  them;  in  donkeys, 
from  only  a  few  being  kept  by  poor  people,  and  little  atten¬ 
tion  paid  to  their  breeding;  for  recently  in  certain  parts  of 
Spain  and  of  the  United  States  this  animal  has  been  sur¬ 
prisingly  modified  and  improved  by  careful  selection;  in 
peacocks,  from  not  being  very  easily  reared  and  a  large 
stock  not  kept:  in  geese,  from  being  valuable  only  for  two 
purposes,  food  and  feathers,  and  more  especially  from  no 
pleasure  having  been  felt  in  the  display  of  distinct  breeds; 
but  the  goose,  under  the  conditions  to  which  it  is  exposed 
when  domesticated,  seems  to  have  a  singularly  inflexible 
organization,  though  it  has  varied  to  a  slight  extent,  as  I 
have  elsewhere  described. 

Some  authors  have  maintained  that  the  amount  of  varia¬ 
tion  in  our  domestic  productions  is  soon  reached,  and  can 
never  afterward  be  exceeded.  It  would  be  somewhat  rash 
to  assert  that  the  limit  has  been  attained  in  any  one  case; 
for  almost  all  our  animals  and  plants  have  been  greatly  im¬ 
proved  in  many  ways  within  a  recent  period;  and  this  im¬ 
plies  variation.  It  would  be  equally  rash  to  assert  that 
characters  nowfincreased  to  their  utmost  limit,  could  not, 
after  remaining  fixed  for  many  centuries,  again  vary  under 
new  conditions  of  life.  No  doubt,  as  Mr.  Wallace  has  re¬ 
marked  with  much  truth,  a  limit  will  be  at  last  reached. 
For  instance,  there  must  be  a  limit  to  the  fleetness  of  any 
terrestrial  animal,  as  this  will  be  determined  by  the  fric¬ 
tion  to  be  overcome,  the  weight  of  the  body  to  be  carried, 
and  the  power  of  contraction  in  the  muscular  fibers.  But 


CIRCUMSTANCES  FAVORABLE  TO  SELECTION.  37 


what  concerns  us  is  that  the  domestic  varieties  of  the  same 
species  differ  from  each  other  in  almost  every  character, 
which  man  has  attended  to  and  selected,  more  than  do  the 
distinct  species  of  the  same  genera.  Isidore  Geoff roy  St. 
Hilaire  has  proved  this  in  regard  to  size,  and  so  it  is  with 
color,  and  probably  with  the  length  of  hair.  With  respect 
to  fleetness,  which  depends  on  many  bodily  characters. 
Eclipse  was  far  fleeter,  and  a  dray-horse  is  comparably 
stronger,  than  any  two  natural  species  belonging  to  the  same 
genus.  So  with  plants,  the  seeds  of  the  different  varieties 
of  the  bean  or  maize  probably  differ  more  in  size  than  do 
the  seeds  of  the  distinct  species  in  any  one  genus  in  the 
same  two  families.'  The  same  remark  holds  good  in  regard 
to  the  fruit  of  the  several  varieties  of  the  plum,  and  still 
more  strongly  with  the  melon,  as  well  as  in  many  other 
analogous  cases. 

To  sum  up  on  the  origin  of  our  domestic  races  of  ani¬ 
mals  and  plants.  Changed  conditions  of  life  are  of  the 
highest  importance  in  causing  variability,  both  by  acting 
directly  on  the  organization,  and  indirectly  by  affecting  the 
reproductive  system.  It  is  not  probable  that  variability  is 
an  inherent  and  necessary  contingent,  under  all  circum¬ 
stances.  The  greater  or  less  force  of  inheritance  and 
reversion  determine  whether  variations  shall  endure. 
Variability  is  governed  by  many  unknown  laws,  of  which 
correlated  growth  is  probably  the  most  important.  Some¬ 
thing,  but  how  much  we  do  not  know,  may  be  attributed 
to  the  definite  action  of  the  conditions  of  life.  Some,  per¬ 
haps  a  great,  effect  may  be  attributed  to  the  increased  use 
or  disuse  of  parts.  The  final  result  is  thus  rendered 
infinitely  complex.  In  some  cases  the  intercrossing  of 
aboriginally  distinct  species  appears  to  have  played  an 
important  part  in  the  origin  of  our  breeds.  When  several 
breeds  have  once  been  formed  in  any  country,  their  occa 
sional  intercrossing,  with  the  aid  of  selection,  has,  no 
doubt,  largely  aided  in  the  formation  of  new  sub-breeds; 
but  the  importance  of  crossing  has  been  much  exaggerated, 
both  in  regard  to  animals  and  to  those  plants  which  are 
propagated  by  seed.  With  plants  which  are  temporarily 
propagated  by  cuttings,  buds,  etc.,  the  importance  of  cross¬ 
ing  is  immense;  for  the  cultivator  may  here  disregard  the 
extreme  variability  both  ©£  hybrids  and  of  mongrels,  and 


38  CIRCUMSTANCES  FAVORABLE  TO  SELECTION. 


the  sterility  of  hybirds;  but  plants  not  propagated  by  seed 
are  of  little  importance  to  us,  for  their  endurance  is  only 
temporary.  Over  all  these  causes  of  change,  the  accumu¬ 
lative  action  of  selection,  whether  applied  methodically 
and  quickly,  or  unconsciously  and  slowly,  but  more 
efficiently,  seems  to  have  been  the  predominant  power. 


VARIATION  UNDER  NATURE, 


CHAPTER  II. 

VARIATION  UNDER  NATURE. 

Variability — Individual  differences — Doubtful  species — Wide  rang, 
ing,  much  diffused,  and  common  species,  vary  most — Species  of 
tbe  larger  genera  in  each  country  vary  more  frequently  than 
the  species  of  the  smaller  genera — Many  of  the  species  of  tli9 
larger  genera  resemble  varieties  in  being  very  closely,  but  un¬ 
equally,  related  to  each.  other,  and  in  having  restricted  ranges. 

Before  applying  the  principles  arrived  at  in  the  last 
chapter  to  organic  beings  in  a  state  of  nature,  we  must 
briefly  discuss  whether  these  latter  are  subject  to  any 
variation.  To  treat  this  subject  properly,  a  long  catalogue 
of  dry  facts  ought  to  be  given;  but  these  I  shall  reserve  for 
a  future  work.  Nor  shall  I  here  discuss  the  various  defini¬ 
tions  which  have  been  given  of  the  term  species.  No  one 
definition  has  satisfied  all  naturalists;  yet  every  naturalist 
knows  vaguely  what  he  means  when  he  speaks  of  a  species. 
Generally  the  term  includes  the  unknown  element  of  s 
distinct  act  of  creation.  The  term  “variety”  is  almost 
equally  difficult  to  define;  but  here  community  of  descent 
is  almost  universally  implied,  though  it  can  rarely  be 
proved.  We  have  also  what  are  called  monstrosities;  but 
they  graduate  into  varieties.  By  a  monstrosity  I  presume 
is  meant  some  considerable  deviation  of  structure,  gener¬ 
ally  injurious,  or  not  useful  to  the  species.  Some  authors 
use  the  term  “variation”  in  a  technical  sense,  as  implying 
a  modification  directly  due  to  the  physical  conditions  of 
life;  and  “variations”  in  this  sense  are  supposed  not  to  be 
inherited;  but  who  can  say  that  the  dwarfed  condition  of 
shells  in  the  brackish  waters  of  the  Baltic,  or  dwarfed 
plants  on  Alpine  summits,  or  the  thicker  fur  of  an  animal 
from  far  northward,  would  not  in  some  cases  be  inherited 
for  at  least  a  few  generations?  And  in  this  case  I  presume 
that  the  form  would  be  called  a.  variety. 


INDIVIDUAL  DIFFERENCES. 

It  may  be  doubted  whether  sudden  and  considerable 
deviations  of  structure,  such  as  we  occasionally  see  in  our 
domestic  productions,  more  especially  with  plants,  are  ever 
permanently  propagated  in  a  state  of  nature.  Almost 
every  part  of  every  organic  being  is  so  beautifully  related 
to  its  complex  conditions  of  life  that  it  seems  as  improbable 
that  any  part  should  have  been  suddenly  produced  peifect, 
as  that  a  complex  machine  should  have  been  invented  by 
man  in  a  perfect  state.  Under  domestication  monstrosi¬ 
ties  sometimes  occur  which  resemble  normal  stiuctures  in 
widely  different  animals.  Thus  pigs  have  occasionally  been 
bom  with  a  sort  of  proboscis,  and  if  any  wild  species  of  the 
same  genus  had  naturally  possessed  a  proboscis,  it  might 
have  been  argued  that  this  had  appeared  as  a  monstrosity , 
but  I  have  as  yet  failed  to  find,  after  diligent  search,  cases 
of  monstrosities  resembling  normal  structures  in  nearly 
allied  forms,  and  these  alone  bear  on  the  question.  If 
monstrous  forms  of  this  kind  ever  do  appear  in  a  state  ot 
nature  and  are  capable  of  reproduction  (which  is  riot 
always  the  case),  as  they  occur  rarely  and  singly,  then- 
preservation  would  depend  on  unusually  favorable  circum¬ 
stances.  They  would,  also,  during  the  first  and  succeeding 
venerations  cross  with  the  ordinary  form,  and  thus  then 
abnormal  character  would  almost  inevitably  be  lost.  Hut 
I  shall  have  to  return  in  a  future  chapter  to  the  preserva¬ 
tion  and  perpetuation  of  single  or  occasional  variations. 

INDIVIDUAL  DIFFERENCES. 

The  many  slight  differences  which  appear  in  the  offspring 
from  the  same  parents,  or  which  it  may  be  presumed  have 
thus  arisen,  from  being  observed  in  the  individuals  of  the 
same  species  inhabiting  the  same  confined  locality,  may  be 
called  individual  differences.  No  one  supposes  that  all 
the  individuals  of  the  same  species  are  cast  in  the  same 
.actual  mold.  These  individual  differences  aie  of  the 
/(highest  importance  for  us,  for  they  are  often  inherited,  as 
(must  be  familiar  to  every  one;  and  they  thus  afford  mate- 
I  rials  for  natural  selection  to  act  on  and  accumulate,  m  the 
/  same  manner  as  man  accumulates  in  any  given  diiection 
I  individual  differences  in  his  domesticated  pioductions. 
i  These  xndividual  differences  generally  affect  what  naturalists 


INDIVIDUAL  DIFFERENCES. 


41 


consider  unimportant  parts;  but  I  could  show,  by  a  long 
catalogue  of  facts,  that  parts  which  must  be  called  important, 
whether  viewed  under  a  physiological  or  classificatory  point 
of  view,  sometimes  vary  in  the  individuals  of  the  same 
species.  I  am  convinced  that  the  most  experienced  natu¬ 
ralist  would  be  surprised  at  the  number  of  the  cases  of 
variability,  even  in  important  parts  of  structure,  which  he 
could  collect  on  good  authority,  as  I  have  collected,  during 
a  course  of  years.  &  It  should  be  remembered  that  systema- 
tists  are  far  from  being  pleased  at  finding  variability  in 
important  characters,  and  that  there  are  not  many  men 
who  will  laboriously  examine  internal  and  important 
organs,  and  compare  them  in  many  specimens  of  the  same 
species.  It  would  never  have  been  expected  that  the 
branching  of  the  main  nerves  close  to  the  great  central 
ganglion  of  an  insect  would  have  been  variable  in  the  same 
species;  it  might  have  been  thought  that  changes  of  this 
nature  could  have  been  effected  only  by  slow  degrees;  yet 
Sir  J.  Lubbock  has  shown  a  degree  of  variability  in  these 
main  nerves  in  Coccus,  which  may  almost  be  compared  to 
the  irregular  branching  of  the  stem  of  a  tree.  This  philo¬ 
sophical  naturalist,  I  may  add,  has  also  shown  that  the 
muscles  in  the  larvas  of  certain  insects  are  far  from  uni¬ 
form.  Authors  sometimes  argue  in  a  circle  when  they 
state  that  important  organs  never  vary;  for  these  same 
authors  practically  rank  those  parts  as  important  (as  some 
few  naturalists  have  honestly  confessed)  which  do  not  vary; 
and,  under  this  point  of  view,  no  instance  will  ever  be 
found  of  an  important  part  varying;  but  under  any  other 
point  of  view  many  instances  assuredly  can  be  given* 

There  is  one  point  connected  with  individual  differences 
which  is  extremely  perplexing  :  I  refer  to  those  genera 
which  have  been  called  “  protean”  or  “  polymorphic,”  in 
which  species  present  an  inordinate  amount  of  variation. 
With  respect  to  many  of  these  forms,  hardly  two  naturalists 
agree  whether  to  rank  them  as  species  or  as  varieties.  We 
may  instance  Rubus,  Rosa,  and  Hieracium  among  plants, 
several  genera  of  insects  and  of  Brachiopod  shells.  In 
most  polymorphic  genera  some  of  the  species  have  fixed 
and  definite  characters.  Genera  which  are  polymorphic  in 
one  country  seem  to  be,  with  a  few  exceptions,  polymorphic 
in  other  countries,  and  likewise,  judging  from  Brachiopod 


42 


INDIVIDUAL  DIFFERENCES. 


shells,  at  former  periods  of  time.  These  facts  are  ver> 
perplexing,  for  they  seem  to  show  that  this  kind  of  varia¬ 
bility  is  independent  of  the  conditions  of  life.  I  am  in¬ 
clined  to  suspect  that  we  see,  at  least  in  some  of  these 
polymorphic  genera,  variations  which  are  of  no  service  or 
disservice  to  the  species,  and  which  consequently  have  not 
been  seized  on  and  rendered  definite  by  natural  selection, 
as  hereafter  to  be  explained. 

*  Individuals  of  the  same  species  often  present,  as  is 
I  known  to  every  one,  great  differences  of  structure,  in- 
I  dependency  of  variation,  as  in  the  two  sexes  of  various 
)  animals,  in  the  two  or  three  castes  of  sterile  females  or 
workers  among  insects,  and  in  the  immature  and  larval 
states  of  many  of  the  lower  animals.  /  There  are,  also,  cases 
of  dimorphism  and  trimorphism,  both  with  animals  and 
plants.  Thus,  Mr.  Wallace,  who  has  lately  called  attention 
to  the  subject,  has  shown  that  the  females  of  certain 
species  of  butterflies,  in  the  Malayan  Archipelago,  reg¬ 
ularly  appear  under  two  or  even  three  conspicuously  dis¬ 
tinct  forms,  not  connected  by  intermediate  varieties.  Fritz 
Muller  has  described  analogous  but  more  extraordinary 
cases  with  the  males  of  certain  Brazilian  Crustaceans:  thus, 
the  male  of  a  Tanais  regularly  occurs  under  two  distinct 
forms;  one  of  these  has  strong  and  differently  shaped 
pincers,  and  the  other  has  antennae  much  more  abundantly 
furnished  with  smelling-hairs.  Although  in  most  of  these 
cases,  the  two  or  three  forms,  both  with  animals  and  plants, 
are  not  now  connected  by  intermediate  gradations,  it  is 
probable  that  they  were  once  thus  connected.  Mr.  Wallace, 
for  instance,  describes  a  certain  butterfly  which  presents  in 
the  same  island  a  great  range  of  varieties  connected  by  in¬ 
termediate  links,  and  the  extreme  links  of  the  chain  closely 
resemble  the  two  forms  of  an  allied  dimorphic  species  in¬ 
habiting  another  part  of  the  Malay  Archipelago.  Thus 
also  with  ants,  the  several  worker-castes  are  generally  quite 
distinct;  but  in  some  cases,  as  we  shall  hereafter  see,  the 
castes  are  connected  together  by  finely  graduated  varieties. 
So  it  is,  as  I  have  myself  observed,  with  some  dimorphic 
plants.  It  certainly  at  first  appears  a  highly  remarkable 
fact  that  the  same  female  butterfly  should  have  the  power 
of  producing  at  the  same  time  three  distinct  female  forms 
and  a  male;  and  that  an  hermaphrodite  plant  shouM  pro- 


DOUBTFUL  SPECIES.  43 

nhrorlulT  the  ®am.e  seed-capsule  three  distinct  herma- 
p  nodite  foims,  bearing  three  different  kinds  of  females  and 
three  or  even  six  different  kinds  of  males.  Nevertheless 
these  cases  are  only  exaggerations  of  the  common  fact  that 

Produoes,  offspring  of  two  sexes  which  some- 
times  differ  from  each  other  in  a  wonderful  manner. 

DOUBTFUL  SPECIES. 

The  forms  which  possess  in  some  considerable  degree 

to*  otherCtfo  °f  Speoles>  but  which  “e  so  closely  similar 
to  other  forms  or  are  so  closely  linked  to  them  bv 

rank'Them  1rUr  tl0inS’  tbat  natnralists  do  not  like  to 
most  11?  species,  are  in  several  respects  the 
,  r  nnpoitant  for  us.  We  have  every  reason  to 

fm  enthat  many  °f  these  do«btful  and  closely  allied 

lon™time^efoPeim£inently  1„etained  their  character  for  a 
f  P  ®’  fo1  ,as  Io>ig,  as  far  as  we  know,  as  have  good 

unffe  bv®  ,rCleS-  ,  Pl;actica11^  when  a  naturalist  §can 
unite  by  means  of  intermediate  links  any  two  forms  he 

common6  but  &<?  &  ?-riety  t°,f  the  otber;  ranking  the  most 
““OD’  ll‘  sometimes  the  one  first  described  as  the 

diffienltv  i-hi  T  hen  lhe  variety-  But  cases  of  great 
in  deohW  WI  notbere  enumerate,  sometimes  arise 
m  deciding  whether  or  not  to  rank  one  form  as  a  variety 

of  another,  even  when  they  are  closely  connected  Vmtel 

/|  late  J ll“ks’.  nor  will  the  commonly  assumed  ^hybrid 

cnftv  Tut  l6  mtermedlate  forms  always  remove  the  diffi¬ 
culty.  in  veiy  many  cases.  However,  one  form  is  ranked 

WeTctaallv  han0tter’  ?0ti  b!Tae  the  iuformediate  links 
nave  actually  been  found,  but  because  analogy  leads  the 

exist^or  mav  ^g1086,  ^  they  do  nof  somewhere 

for  the  e^t,  J  n? ’f  exlstedi  and  here  a  wide  door 
for  the  cntiy  of  doubt  and  conjecture  is  opened. 

lnce’.  m  determining  whether  a  form  should  be  ranked  j 

“  or  *  vai’iety,  the  opinion  of  naturalists  having  » 

to  foflowdg  We  *  “  f  'Ilde  exPeidenoe  seems  the  only  guidf 
to  follow.  We  must,  however,  in  many  cases,  decide  bv  a 

kT?n°nty  °.f  natllrat|sts,  for  few  well-marked  and  well- 

as  sned^hv  ieMCanfbe  named  Whicb  have  Bot  been  ranked 
as  species  by  at  least  some  competent  -judges. 

dhat  varieties  of  this  doubtful  nature  are  far  f*om 


44 


DOUBTFUL  SPECIES. 


uncommon  cannot  be  disputed.  Compare  the  several  floras 
of  Great  Britain,  of  France,  or  of  the  United  States,  drawn 
up  by  different  botanists,  and  see  what  a  surprising  num¬ 
ber  of  forms  have  been  ranked  by  one  botanist  as  good 
species,  and  by  another  as  mere  varieties.  Mr.  H.  C. 
Watson,  to  whom  I  lie  under  deep  obligation  for  assistance 
of  all  kinds,  has  marked  for  me  182  British  plants,  which 
are  generally  considered  as  varieties,  but  which  have  all 
been  ranked  by  botanists  as  species;  and  in  making  this 
list  he  has  omitted  many  trifling  varieties,  but  which  never¬ 
theless  have  been  ranked  by  some  botanists  as  species,  and 
he  has  entirely  omitted  several  highly  polymorphic  genera. 
Under  genera,  including  the  most  polymorphic  forms,  Mr. 
Babington  gives  251  species,  whereas  Mr.  Bentham  gives 
only  112 — a  difference  of  139  doubtful  forms!  Among 
animals  which  unite  for  each  birth,  and  which  are  highly 
locomotive,  doubtful  forms,  ranked  by  one  zoologist  as  a 
species  and  by  another  as  a  variety,  can  rarely  be  found 
within  the  same  country,  but  are  common  in  separated 
areas.  How  many  of  the  birds  and  insects  in  North 
America  and  Europe,  which  differ  very  slightly  from  each 
other,  have  been  ranked  by  one  eminent  naturalist  as  un¬ 
doubted  species,  and  by  another  as  varieties,  or,  as  they 
are  often  called,  geographical  races !  Mr.  Wallace,  in 
several  valuable  papers  on  the  various  animals,  especially 
on  the  Lepidoptera,  inhabiting  the  islands  of  the  great 
Malayan  Archipelago,  shows  that  they  may  be  classed  under 
four  heads,  namely,  as  variable  forms,  as  local  forms,  as 
geographical  races  or  sub-species,  and  as  true  representa¬ 
tive  species.  The  first  or  variable  forms  vary  much  within 
the  limits  of  the  same  island.  The  local  forms  are  moder¬ 
ately  constant  and  distinct  in  each  separate  island;  but 
when  all  from  the  several  islands  are  compared  together, 
the  differences  are  seen  to  be  so  slight  and  graduated  that 
it  is  impossible  to  define  or  describe  them,  though  at  the 
same  time  the  extreme  forms  are  sufficiently  distinct. 
The  geographical  races  or  sub-species  are  local  forms 
completely  fixed  and  isolated ;  but  as  they  do  not 
differ  from  each  other  by  strongly  marked  and 
important  characters,  <(  There  is  no  possible  test  but 
individual  opinion  to  determine  wffiich  of  them  shall  be 
considered  as  species  and  which  as  varieties.”  Lastly, 


DOUBTFUL  SPECIES. 


45 


representative  species  fill  the  same  place  in  the  natural 
economy  of  each  island  as  do  the  local  forms  and  sub¬ 
species;  but  as  they  are  distinguished  from  each  other  by  a 
greater  amount  of  difference  than  that  between  the  local 
forms  and  sub-species,  they  are  almost  universally  ranked 
by  naturalists  as  true  species.  Nevertheless,  no  certain 
criterion  can  possibly  be  given  by  which  variable  forms, 
local  forms,  sub-species  and  representative  species  can  be 
recognized. 

Many  years  ago,  when  comparing,  and  seeing  others  com¬ 
pare,  the  birds  from  the  closely  neighboring  islands  of  the 
Galapagcs  Archipelago,  one  with  another,  and  with  those 
from  the  American  mainland,  I  was  much  struck  how  en¬ 
tirely  vague  and  arbitrary  is  the  distinction  between  species 
and  varieties.  On  the  islets  of  the  little  Maderia  group 
there  are  many  insects  which  are  characterized  as 
varieties  in  Mr.  Wollaston’s  admirable  work,  but  which 
would  certainly  be  ranked  as  distinct  species  by  many  en¬ 
tomologists.  Even  Ireland  has  a  few  animals,  now  gen¬ 
erally  regarded  as  varieties,  but  which  have  been  ranked  as 
species  by  some  zoologists.  Several  experienced  ornitholo¬ 
gists  consider  our  British  red  grouse  as  only  a  strongly 
marked  race  of  a  Norwegian  species,  whereas  the  greater 
number  rank  it  as  an  undoubted  species  peculiar  to  Great 
Britain.  A  wide  distance  between  the  homes  of  two  doubt¬ 
ful  forms  leads  many  naturalists  to  rank  them  as  distinct 
species;  but  what  distance,  it  has  been  well  asked,  will  suf¬ 
fice  if  that  between  America  and  Europe  is  ample,  will  that 
between  Europe  and  the  Azores,  or  Maderia,  or  the  Cana¬ 
ries,  or  between  the  several  islets  of  these  small  archipelagos, 
be  sufficient? 

Mr.  B.  D.  Walsh,  a  distinguished  entomologist  of  the 
United  States,  has  described  what  he  calls  Phytophagic 
varieties  and  Phytophagic  species.  Most  vegetable-feeding 
insects  live  on  one  kind  of  plant  or  on  one  group  of  plants; 
some  feed  indiscriminately  on  many  kinds,  but  do  not  in 
consequence  vary.  In  several  cases,  however,  insects 
found  living  on  different  plants,  have  been  observed  by 
Mr.  Walsh  to  present  in  their  larval  or  mature  state,  or  in 
both  states,  slight,  though  constant  differences  in  color, 
size,  or  in  the  nature  of  their  secretions.  In  some  instances 
the  males  alone,  in  other  instances,  both  males  and  females. 


46 


DOUBTFUL  SPE0IE8. 


have  been  observed  thus  to  differ  in  a  slight  degree.  When 
the  differences  are  rather  more  strongly  marked,  and  when 
both  sexes  and  all  ages  are  affected,  the  forms  are  ranked 
by  all  entomologists  as  good  species.  But  no  observer  can 
determine  for  another,  even  if  he  can  do  so  for  himself, 
which  of  these  Phytophagic  forms  ought  to  be  called 
species  and  which  varieties.  Mr.  Walsh  ranks  the  forms 
which  it  may  be  supposed  would  freely  intercross,  as  varie¬ 
ties;  and  those  which  appear  to  have  lost  this  power,  as 
species.  As  the  differences  depend  on  the  insects  having 
long  fed  on  distinct  plants,  it  can  not  be  expected  that 
intermediate  links  connecting  the  several  forms  should 
now  be  found.  The  naturalist  thus  loses  his  best  guide  in 
determining  whether  to  rank  doubtful  forms  as  varieties 
or  species.  This  likewise  necessarily  occurs  with  closely 
allied  organisms,  which  inhabit  distinct  continents  or 
islands.  When,  on  the  other  hand,  an  animal  or  plant 
ranges  over  the  same  continent,  or  inhabits  many  islands  in 
the  same  archipelago,  and  presents  different  forms  in  the 
different  areas,  there  is  always  a  good  chance  that  inter¬ 
mediate  forms  will  be  discovered  which  will  link  together 
the  extreme  states;  and  these  are  then  degraded  to  the 
rank  of  varieties. 

Some  few  naturalists  maintain  that  animals  never  pre¬ 
sent  varieties;  but  then  these  same  naturalists  rank  the 
slightest  difference  as  of  specific  value;  and  when  the  same 
identical  form  is  met  with  in  two  distant  countries,  or  in 
two  geological  formations,  they  believe  that  two  distinct 
species  are  hidden  under  the  same  dress.  The  term 
species  thus  comes  to  be  a  mere  useless  abstraction,  imply¬ 
ing  and  assuming  a  separate  act  of  creation.  It  is  certain 
that  many  forms,  considered  by  highly  competent  judges 
to  be  varieties,  resemble  species  so  completely  in  character 
that  they  have  been  thus  ranked  by  other  highly  compe¬ 
tent  judges.  But  to  discuss  whether  they  ought  to  be 
called  species  or  varieties,  before  any  definition  of  these 
terms  has  been  generally  accepted,  is  vainly  to  beat  the  air*. 

Many  of  the  cases  of  strongly  marked  varieties  or  doubt¬ 
ful  species  well  deserve  consideration;  for  several  interest¬ 
ing  lines  of  argument,  from  geographical  distribution, 
analogical  variation,  hybridism,  etc.,  have  been  brought  to 
bear  in  the  attempt  to  determine  their  rank;  but  space 


.  DOUBTFUL  SPECIES. 


47 


does  not  here  permit  me  to  discuss  them.  Close  investiga¬ 
tion,  in  many  cases,  will  no  doubt  bring  naturalists  to  agree 
how  to  rank  doubtful  forms.  Yet  it  must  be  confessed 
that  it  is  in  the  best  known  countries  that  we  find  the 
greatest  number  of  them.  I  have  been  struck  with  the 
fact  that  if  any  animal  or  plant  in  a  state  of  nature  be 
highly  useful  to  man,  or  from  any  cause  closely  attracts 
his  attention,  varieties  of  it  will  almost  universally  be 
found  recorded.  These  varieties,  moreover,  will  often  be 
ranked  by  some  authors  as  species.  Look  at  the  common 
oak,  how  closely  it  has  been  studied;  yet  a  German  author 
makes  more  than  a  dozen  species  out  of  forms,  which  are 
almost  universally  considered  by  other  botanists  to  be  vari¬ 
eties;  and  in  this  country  the  highest  botanical  authorities 
and  practical  men  can  be  quoted  to  show  that  the  sessile 
and  pedunculated  oaks  are  either  good  and  distinct  species 
or  mere  varieties. 

I  may  here  allude  to  a  remarkable  memoir  lately  pub¬ 
lished  by  A.  de  Candolle,  on  the  oaks  of  the  whole  world. 
No  one  ever  had  more  ample  materials  for  the  discrimina¬ 
tion  of  the  species,  or  could  have  worked  on  them  with 
more  zeal  and  sagacity.  He  first  gives  in  detail  all  the  many 
points  of  structure  which  vary  in  the  several  species,  and 
estimates  numerically  the  relative  frequency  of  the  vari¬ 
ations.  He  specifies  above  a  dozen  characters  which  may 
be  found  varying  even  on  the  same  branch,  sometimes 
according  to  age  or  development,  sometimes  without 
any  assignable  reason.  Such  characters  are  not  of  course 
of  specific  value,  but  they  are,  as  Asa  Gray  has  remarked 
in  commenting  on  this  memoir,  such  as  generally  enter 
into  specific  definitions.  De  Candolle  then  goes  on  to 
say  that  he  gives  the  rank  of  species  to  the  forms  that 
differ  by  characters  never  varying  on  the  same  tree,  and 
never  found  connected  by  intermediate  states.  After 
this  discussion,  the  result  of  so  much  labor,  he 
emphatically  remarks:  “  They  are  mistaken,  who 
repeat  that  the  greater  part  of  our  species  are  clearly 
limited,  and  that  the  doubtful  species  are  in  a  feeble 
minority.  This  seemed  to  be  true,  so  long  as  a  genus  was 
imperfectly  known,  and  its  species  were  founded  upon  a 
few  specimens,  that  is  to  say,  were  provisional.  Just  as 
we  come  to  know  them  better,  intermediate  forms  flow  in, 


48 


DOUBTFUL  SPECIES. 


and  doubts  as  to  specific  limits  augment.”  He  also  adds 
that  it  is  the  best  known  species  which  present  the  greatest 
number  of  spontaneous  varieties  and  sub- varieties.  Thus 
Quercus  robur  has  twenty-eight  varieties,  all  of  which, 
excepting  six,  are  clustered  round  three  sub-species, 
namely  Q.  pedunculata,  sessiliflora  and  pubescens.  The 
forms  which  connect  these  three  sub-species  are  compara¬ 
tively  rare;  and,  as  Asa  Gray  again  remarks,  if  these  con¬ 
necting  forms  which  are  now  rare  were  to  become  totally 
extinct  the  three  sub-species  would  hold  exactly  the  same 
relation  to  each  other  as  do  the  four  or  five  provisionally 
admitted  species  which  closely  surround  the  typical  Quer¬ 
cus  robur.  Finally,  De  Candolle  admits  that  out  of  the  300 
species,  which  will  be)  enumerated  in  his  Prodromus  as 
belonging  to  the  oak  family,  at  least  two-thirds  are  provis¬ 
ional  species,  that  is,  are  not  known  strictly  to  fulfil  the 
definition  above  given  of  a  true  species.  It  should  be 
added  that  De  Candolle  no  longer  believes  that  species 
are  immutable  creations,  but  concludes  that  the  derivative 
theory  is  the  most  natural  one,  “  and  the  most  accordant 
with  the  known  facts  in  palaeontology,  geographical 
botany  and  zoology,  of  anatomical  structure  and  classific¬ 
ation.” 

When  a  young  naturalist  commences  the  study  of  a 
group  of  organisms  quite  unknown  to  him  he  is  at  first 
much  perplexed  in  determining  what  differences  to  consider 
as  specific  and  what  as  varietal;  for  he  knows  nothing  of 
the  amount  and  kind  of  variation  to  which  the  group  is 
subject;  and  this  shows,  at  least,  how  very  generally  there 
is  some  variation.  But  if  he  confine  his  attention  to  one 
class  within  one  country  he  will  soon  make  up  his  mind 
how  to  rank  most  of  the  doubtful  forms.  His  general  ten¬ 
dency  will  be  to  make  many  species,  for  he  will  become 
impressed,  just  like  the  pigeon  or  poultry  fancier  before 
alluded  to,  with  the  amount  of  difference  in  the  forms 
which  he  is  continually  studying;  and  he  has  little  general 
knowledge  of  analogical  variation  in  other  groups  and  in 
other  countries  by  which  to  correct  his  first  impressions. 
As  he  extends  the  range  of  his  observations  he  will  meet 
with  more  cases  of  difficulty;  for  he  will  encounter  a 
greater  number  of  closely  allied  forms.  But  if  his  obser¬ 
vations  be  widely  extended  he  will  in  the  end  generally  be 


DOUBT* uL  SPECIES. 


49 


able  to  make  up  his  own  mind;  but  he  will  succeed  in  this 
at  the  expense  of  admitting  much  variation,  and  the  truth 
of  this  admission  will  often  be  disputed  by  other  natural¬ 
ists.  When  he  comes  to  study  allied  forms  brought  from 
countries  not  now  continuous,  in  which  case  he  cannot 
hope  to  find  intermediate  links,  he  will  be  compelled  to 
trust  almost  entirely  to  analogy,  and  his  difficulties  will 
rise  to  a  climax. 

Certainly  no  clear  line  of  demarcation  has  as  yet  been 
drawn  between  species  and  sub-species — that  is,  the  forms 
which  in  the  opinion  of  some  naturalists  come  very  near 
to,  but  do  not  quite  arrive  at,  the  rank  of  species;  or, 
again,  between  sub-species  and  well-marked  varieties,  or 
between  lesser  varieties  and  individual  differences.  These 
differences  blend  into  each  other  by  an  insensible  series; 
and  a  series  impresses  the  mind  with  the  idea  of  an  actual 
passage. 

Hence  I  look  at  individual  differences,  though  of  small 
interest  to  the  systematist,  as  of  the  highest  importance 
for  us,  as  being  the  first  steps  toward  ^such  slight  varieties 
as  are  barely  thought  worth  recording  in  works  on  natural 
history.  And  I  look  at  varieties  which  are  in  any  degree 
more  distinct  and  permanent,  as  steps  toward  more 
strongly  marked  and  permanent  varieties;  and  at  the  lat¬ 
ter,  as  leading  to  sub-species,  and  then  to  species.  The 
passage  from  one  stage  of  difference  to  another  may,  in 
many  cases,  be  the  simple  result  of  the  nature  of  the 
organism  and  of  the  different  physical  conditions  to  which  it 
has  long  been  exj)osed;  but  with  respect  to  the  more  im¬ 
portant  and  adaptive  characters,  the  passage  from  one  stage 
of  difference  to  another  may  be  safely  attributed  to  the 
cumulative  action  of  natural  selection,  hereafter  to  be  ex¬ 
plained,  and  to  the  effects  of  the  increased  use  or  disuse  of 
parts.  A  well-marked  variety  may  therefore  be  called  an 
incipient  species;  but  whether  this  belief  is  justifiable  must 
be  judged  by  the  weight  of  the  various  facts  and  considera¬ 
tions  to  be  given  throughout  this  work. 

It  need  not  be  supposed  that  all  varieties  or  incipient 
species  attain  the  rank  of  species.  They  may  become  ex¬ 
tinct,  or  they  may  endure  as  varieties  for  very  long  periods, 
as  has  been  shown  to  be  the  case  by  Mr.  Wollaston  with 
the  varieties  of  certain  fossil  land-shells  in  Madeira,  and 


50 


DOMINANT  SPECIES  VARY  MOST. 


with  plants  by  Gaston  cle  Saporta.  If  a  variety  were  to 
flourish  so  as  to  exceed  in  numbers  the  parent  species,  it 
would  then  rank  as  the  species,  and  the  species  as  the 
variety;  or  it  might  come  to  supplant  and  exterminate  the 
parent  species;  or  both  might  co-exist,  and  both  rank  as 
independent  species.  But  we  shall  hereafter  return  to  this 
subject. 

ui  From  these  remarks  it  will  be  seen  that  I  look  at  the 
term  species  as  one  arbitrarily  given,  for  the  sake  of  con¬ 
venience,  to  a  set  of  individuals  closely  resembling  each 
other,  and  that  it  does  not  essentially  differ  from  the  term 
variety,  which  is  given  to  less  distinct  and  more  fluctuating 
forms.  The  term  variety,  again,  in  comparison  with  mere 
individual  differences,  is  also  applied  arbitrarily,  for  con¬ 
venience  sake. 

WIDE-RANGING,  MUCH  DIFFUSED,  AND  COMMON  SPECIES 

VARY  MOST. 

Guided  by  theoretical  considerations,  I  thought  that 
some  interesting  results  might  be  obtained  in  regard  to  the 
nature  and  relations  of  the  species  which  vary  most,  by 
tabulating  all  the  varieties  in  several  well-worked  floras. 
At  first  this  seemed  a  simple  task;  but  Mr.  II.  C.  Watson, 
to  whom  I  am  much  indebted  for  valuable  advice  and 
assistance  on  this  subject,  soon  convinced  me  that  there 
were  many  difficulties,  as  did  subsequently  Dr.  Hooker, 
even  in  stronger  terms.  I  shall  reserve  for  a  future  work 
the  discussion  of  these  difficulties,  and  the  tables  of  the 
proportional  numbers  of  the  varying  species.  Dr.  Hooker 
permits  me  to  add  that  after  having  carefully  read  my 
manuscript,  and  examined  the  tables,  he  thinks  that  the 
following  statements  are  fairly  well  established.  The  whole 
subject,  however,  treated  as  it  necessarily  here  is  with  much 
brevity,  is  rather  perplexing,  and  allusions  cannot  be 
avoided  to  the  “struggle  for  existence,”  “divergence  of 
character,”  and  other  questions,  hereafter  to  be  discussed. 

Alphonso  de  Candolle  and  others  have  shown  that 

I  plants  which  have  very  wide  ranges  generally  present 
varieties;  and  this  might  have  been  expected,  as  they  are 
exposed  to  diverse  physical  conditions,  and  as  they  come 
into  competition  (which,  as  we  shall  hereafter  see,  is  an 
equally  or  more  important  circumstance)  with  different 


SPECIES  OF  LARGER  GENERA  VARIABLE.  51 


sets  of  organic  beings.  But  my  tables  further  show  that, 
in  any  limited  country,  the  species  which  are  the  most 
common,  that  is  abound  most  in  individuals,  and  the 
species  which  are  most  widely  diffused  within  their  own 
country  (and  this  is  a  different  consideration  from  wide 
range,  and  to  a  certain  extent  from  commonness),  oftenest 
give  rise  to  varieties  sufficiently  well-marked  to  have  been 
recorded  in  botanical  works.  Hence  it  is  the  most  flourish¬ 
ing,  or,  as  they  may  be  called,  the  dominant  species — those 
which  range  widely,  are  the  most  diffused  in  their  own 
country,  and  are  the  most  numerous  in  individuals — which 
oftenest  produce  well-marked  varieties,  or,  as  I  consider 
them,  incipient  species.  And  this,  perhaps,  might  have 
been  anticipated;  for,  as  varieties,  in  order  to  become  in 
any  degree  permanent,  necessarily  have  to  struggle  with  the 
other  inhabitants  of  the  country,  the  species  which  are 
already  dominant  will  be  the  most  likely  to  yield  offspring, 
which,  though  in  some  slight  degree  modified,  still  inherit 
those  advantages  that  enabled  their  parents  to  become 
dominant  over  their  compatriots.  In  these  remarks  on 
predominence,  it  should  be  understood  that  reference  is 
made  only  to  the  forms  which  come  into  competition  with 
each  other,  and  more  especially  to  the  members  of  the 
same  genus  or  class  having  nearly  similar  habits  of  life. 
With  respect  to  the  number  of  individuals  or  commonness 
of  species,  the  comparison  of  course  relates  only  to  the 
members  of  the  same  group.  One  of  the  higher  plants 
may  be  said  to  be  dominant  if  it  be  more  numerous  in 
individuals  and  more  widely  diffused  than  the  other  plants 
of  the  same  country,  which  live  under  nearly  the  same 
conditions.  A  plant  of  this  kind  is  not  the  less  dominant 
because  some  conferva  inhabiting  the  water  or  some  para¬ 
sitic  fungus  is  infinitely  more  numerous  in  individuals, 
and  more  widely  diffused.  But  if  the  conferva  or  parasitic 
fungus  exceeds  its  allies  in  the  above  respects,  it  will  then 
be  dominant  within  its  own  class. 

SPECIES  OF  THE  LARGER  GENERA  IN  EACH  COUNTRY 
VARY  MORE  FREQUENTLY  THAN  THE  SPECIES  OF  THE 
SMALLER  GENERA. 

If  the  plants  inhabiting  a  country,  as  described  in  any 
Flora,  be  divided  into  two  equal  masses,  all  those  in  the 


52 


SPECIES  OF  LARGER  GENERA  VARIABLE. 


larger  genera  (i.  e .,  those  including  many  species)  being 
placed  on  one  side,  and  all  those  in  the  smaller  genera  on 
the  other  side,  the  former  will  be  found  to  include  a. some¬ 
what  larger  number  of  the  very  common  and  much  diffused 
or  dominant  species.  This  might  have  been  anticipated, 
for  the  mere  fact  of  many  species  of  the  same  genus  in- 
habiting  any  country,  shows  that  there  is  something  in^ 
the  organic  or  inorganic  conditions  of  that  country  favor¬ 
able  to  the  genus;  and,  consequently,  we  might  have  ex¬ 
pected  to  have  found  in  the  larger  genera,  or  those  includ¬ 
ing  many  species,  a  larger  proportional  number  of  dominant 
species.  But  so  many  causes  tend  to  obscure  this  result,  that 
I  am  surprised  that  my  tables  show  even  a  small  majority 
on  the  side  of  the  larger  genera.  I  will  here  allude  to  only 
two  causes  of  obscurity.  Fresh  water  and  salt-loving 
plants  generally  have  very  wide  ranges  and  are  much  dif¬ 
fused,  but  this  seems  to  be  connected  with  the  nature  of 
the  stations  inhabited  by  them,  and  has  little  or  no  relation 
to  the  size  of,  the  genera  to  which  the.  species  belong. 
Again,  plants  low  in  the  scale  of  organization  are  generally 
much  more  widely  diffused  than  plants  higher  in  the  scale; 
and  here  again  there  is  no  close  relation  to  the  size  of  the 
genera.  The  cause  of  lowly  organized  plants  ranging 
widely  will  be  discussed  in  our  chapter  on  Geographical 
Distribution. 

From  looking  at  (species  as  only  strongly  marked  and 
well-defined  varieties, ;  I  was  led  to  anticipate  that  the 
species  of  the  larger  genera  in  each  country  would  oftener 
present  varieties,  than  the  species  of  the  smaller  genera; 
for  wherever  many  closely  related  species  {i.e.,  species. of 
the  same  genus)  have  been  formed,  many  varieties  or  incip¬ 
ient  species  ought,  as  a  general  rule,  to  be  now  forming. 
Where  many  large  trees  grow,  we  expect  to  find  saplings. 
Where  many  species  of  a  genus  have  been  formed  through 
variation,  circumstances  have  been  favorable  for  variation; 
and  hence  we  might  expect  that  the  circumstances  would 
generally  still  be  favorable  to  variation.  On  the  other 
hand,  if  we  look  at  each  species  as  a  special  act  of  creation, 
there  is  no  apparent  reason  why  more  varieties  should 
occur  in  a  group  having  many  species,  than  in  one  having 

few.  #  I 

To  test  the  truth  of  this  anticipation  I  have  arranged 


SPECIES  OF  LARGER  GENERA . 


53 


che  plants  of  twelve  countries,  and  the  coleopterous  insects 
of  two  districts,  into  two  nearly  equal  masses,  the  species 
of  the  larger  genera  on  one  side,  and  those  of  the  smaller 
genera  on  the  other  side,  and  it  has  invariably  proved  to  be 
the  case  that  a  larger  proportion  of  the  species  on  the  side 
of  the  larger  genera  presented  varieties,  than  on  the  side  of 
the  smaller  genera.  Moreover,  the  species  of  the  large 
genera  which  present  any  varieties,  invariably  present  a 
larger  average  number  of  varieties  than  do  the  species  of 
the  small  genera.  Both  these  results  follow  when  another 
division  is  made,  and  when  all  the  least  genera,  with  from 
only  one  to  four  species,  are  altogether  excluded  from  the 
tables.  These  facts  are  of  plain  signification  on  the  view 
that  species  are  only  strongly  marked  and  permanent 
varieties;  for  wherever  many  species  of  the  same  genus 
have  been  formed,  or  where,  if  we  may  use  the  expression, 
the  manufactory  of  species  has  been  active,  we  ought 
generally  to  find  the  manufactory  still  in  action,  more 
especially  as  we  have  every  reason  to  believe  the  process  of 
manufacturing  new  species  to  be  a  slow  one.  And  this 
certainly  holds  true  if  varieties  be  looked  at  as  incipient 
species;  for  my  tables  clearly  show,  as  a  general  rule,  that, 
wherever  many  species  of  a  genus  have  been  formed,  the 
species  of  that  genus  present  a  number  of  varieties,  that  is, 
of  incipient  species,  beyond  the  average.  It  is  not  that  all 
large  genera  are  now  varying  much,  and  are  thus  increasing 
in  the  number  of  their  species,  or  that  no  small  genera  are 
now  varying  and  increasing;  for  if  this  had  been  so,  it 
would  have  been  fatal  to  my  theory;  inasmuch  as  geology 
plainly  tells  us  that  small  genera  have  in  the  lapse  of  time 
often  increased  greatly  in  size;  and  that  large  genera  have 
often  come  to  their  maxima,  decline,  and  disappeared. 
All  that  we  want  to  show  is,  that  where  many  species  of  a 
genus  have  been  formed,  on  an  average  many  are  still 
forming;  and  this  certainly  holds  good. 


MANY  OF  THE  SPECIES  INCLUDED  WITHIN  THE  LARGER 
GENERA  RESEMBLE  VARIETIES  IN  BEING  VERY  CLOSELY, 
BUT  UNEQUALLY,  RELATED  TO  EACH  OTHER,  AND  IN 
HAVING  RESTRICTED  RANGES. 

There  are  other  relations  between  the  species  of  large 


54 


SPECIES  OF  LARGER  GENERA. 


genera  and  their  recorded  varieties  which  deserve  notice. 
We  have  seen  that  there  is  no  infallible  criterion  by  which 
to  distinguish  species  and  well-marked  varieties;  and  when 
intermediate  links  have  not  been  found  between  doubtful 
forms,  naturalists  are  compelled  to  come  to  a  determination 
by  the  amount  of  difference  between  them,  judgingby  anal¬ 
ogy  whether  or  not  the  amount  suffices  to  raise  one  or  both  to 
the  rank  of  species,  j  Hence  the  amount  of  difference  is  one 
very  important  criterion  in  settling  whether  two  forms 
should  be  ranked  as  species  or  varieties.  Now  Fries  has 
remarked  in  regard  to  plants,  and  Westwood  in  regard  to 
insects,  that  in  large  genera  the  amount  of  difference 
between  the  species  is  often  exceedingly  small.  I  have 
endeavored  to  test  this  numerically  by  averages,  and,  as  far 
as  my  imperfect  results  go,  they  confirm  the  view.  I  have 
also  consulted  some  sagacious  and  experienced  observers, 
and,  after  deliberation,  they  concur  in  this  view.  In  this 
respect,  therefore,  the  species  of  the  larger  genera  resemble 
varieties,  more  than  do  the  species  of  the  smaller  genera. 
Or  the  case  may  be  put  in  another  way,  and  it  may  be  said, 
that  in  the  larger  genera,  in  which  a  number  of  varieties  or 
I  incipient  species  greater  than  the  average  are  now  manu- 
l  facturing,  many  of  the  species  already  manufactured  still 
:  to  a  certain  extent  resemble  varieties,  for  they  differ  from 
each  other  by  less  than  the  usual  amount  of  difference. 

Moreover,  the  species  of  the  larger  genera  are  related  to  each 
other,  in  the  same  manner  as  the  varieties  of  anyone  species 
are  related  to  each  other.  No  naturalist  pretends  that  all 
the  species  of  a  genus  are  equally  distinct  from  each  other; 
they  may  generally  be  divided  into  sub-genera,  or  sections, 
or  lesser  groups.  As  Fries  has  well  remarked,  little 
groups  of  species  are  generally  clustered  like  satellites 
around  other  species.  And  what  are  varieties  but  groups 
of  forms,  unequally  related  to  each  other,  and  clustered 
round  certain  forms — that  is,  round  their  parent  species. 
Undoubtedly  there  is  one  most  important  point  of  differ¬ 
ence  between  varieties  and  species,  namely,  that  the 
'amount  of  difference  between  varieties,  when  compared 
with  each  other  or  with  their  parent  species,  is  much  less 
.than  that  between  the  species  of  the  same  genus.  But  when 
we  come  to  discuss  the  principle,  as  I  call  it,  of  divergence 
of  character,  we  shall  see  bow  this  may  be  explained,  and 


55 


RESEMBLE  VARIETIES. 

how  the  lesser  differences  between  varieties  tend  to  increase 
into  the  greater  differences  between  species. 

There  is  one  other  point  which  is  worth  notice.  Varie¬ 
ties  generally  have  much  restricted  ranges.  This  state¬ 
ment  is  indeed  scarcely  more  than  a  truism,  for,  if  a 
vanetv  were  found  to  have  a  wider  range  than  that 
ot  its  supposed  parent  species,  their  denominations 
would  be  reversed  But  there  is  reason  to  believe 
that,  the  species  which  are  very  closely  allied  to  other 
species,  and  m  so  far  resemble  varieties,  often  have  much 
restricted  ranges..  For  instance,  Mr.  H.  C.  Watson  has 
marked  for  me  m  the  well-sifted  London  catalogue  of 
Fiants  (4th  edition)  sixty-three  plants  which  are  therein 
ianked  as  species,  but  which  he  considers  as  so  closelv 
allied  to  other  species  as  to  be  of  doubtful  value:  these 
sixty-three  reputed  species  range  on  an  average  over  6.9 
of  the  provinces  into  which  Mr.  Watson  has  divided 
Lieat  Britain.  Now,  in  this  same  catalogue,  fifty- 
three  acknowledged  varieties  are  recorded,  and  these 
range  over  7.7  provinces;  whereas,  the  species  to  which 
™netles  Mon g  range  over  14.3  provinces.  So 
that  the  acknowledged  varieties  have  nearly  the  same 
restricted  average  range,  as  have  the  closely  allied  forms, 
marked  for  me  by  Mr.  Watson  as  doubtful  species,  but 
which  are  almost  universally  ranked  by  British  botanists 
as  good  and  true  species. 


SUMMARY. 

Finally,  varieties  cannot  be  distinguished  f»om  species, 
--except,  first,  by  the  discovery  of.  intermediate  linking’ 
forms;  and,  secondly,  by  a  certain  indefinite  amount  of 
difference  between  them;  for  two  forms,  if  differing  very 
little  are  generally  ranked  as  varieties,  notwithstanding 
that  they  cannot  be  closely  connected;  but  the  amount  of 
difference  considered  necessary  to  give  to  any  two  forms 
the  rank  of  species  cannot  be  defined.  In  genera  havino- 
more  than  the  average  number  of  species  in  any  country, 
tne  species  of  .  these  genera  have  more  than  the  average 
number  of  varieties.  In  large  genera  the  species  are  apt 
to  be  closely  but  unequally  allied  together,  forming  little 
dusters  round  other  species.  Species  very  closely  allied  to 


56 


RESEMBLE  VARIETIES. 


other  species  apparently  have  restricted  ranges.  In  all 
these  respects  the  species  of  large  genera  present  a  strong 
analogy  with  varieties.  And  we  can  clearly  understand 
these  analogies,  if  species  once  existed  as  varieties,  and 
thus  originated;  whereas,  these  analogies  are  utterly  inex¬ 
plicable  if  species  are  independent  creations. 

We  have  also  seen  that  it  is  the  most  flourishing  or  domi¬ 
nant  species  of  the  larger  genera  within  each  class  which 
on  an  average  yield  the  greatest  nurffber  of  varieties;  and 
varieties,  as  we  shall  hereafter  see,  tend  to  become  con¬ 
verted  into  new  and  distinct  species.  Thus  the  larger 
genera  tend  to  become  larger;  and  throughout  nature  the 
forms  of  life  which  are  ^ow  dominant  tend  to  become  still 
more  dominant  by  leaving  many  modified  and  dominant 
descendants.  But,  by  steps  hereafter  to  be  explained,,  the 
larger  genera  also  tend  to  break  up  into  smaller  genera. 
And  thus,  the  forms  of  life  throughout  the  universe  be¬ 
come  divided  into  groups  subordinate  to  groups. 


STRUGGLE  FOR  EXISTENCE. 


57 


CHAPTER  III. 

STRUGGLE  FOR  EXISTENCE. 

Its  bearing  on  natural  selection— The  term  used  in  a  wide  sense — 
Geometrical  ratio  of  increase — Rapid  increase  of  naturalized 
animals  and  plants — Nature  of  the  checks  to  increase — Com¬ 
petition  universal — Effects  of  climate — Protection  from  the 
number  of  individuals — Complex  relations  of  all  animals  and 
plants  throughout  nature — Struggle  for  life  most  severe  between 
individuals  and  varieties  of  the  same  species:  often  severe 
between  species  of  the  same  genus — The  relation  of  organism 
to  organism  the  most  important  of  all  relations. 

Before  entering  on  the  subject  of  this  chapter  I  must 
make  a  few  preliminary  remarks  to  show  how  the  struggle 
for  existence  bears  on  natural  selection.  It  has  been  seen 
in  the  last  chapter  that  among  organic  beings  in  a  state  of 
nature  there  is  some  individual  variability:  indeed  I  am 
not  aware  that  this  has  ever  been  disputed.  It  is  imma¬ 
terial  for  us  whether  a  multitude  of  doubtful  forms  be 
called  species  or  sub-species  or  varieties;  what  rank,  for 
instance,  the  two  or  three  hundred  doubtful  forms  of 
British  plants  are  entitled  to  hold,  if  the  existence  of  any 
well-marked  varieties  be  admitted.  But  the  mere  exist¬ 
ence  of  individual  variability  and  of  some  few  well-marked 
varieties,  though  necessary  as  the  foundation  for  the  work, 
helps  us  but  little  in  understanding  how  species  arise  in 
nature.  How  have  all  those  exquisite  adaptations  of  one 
part  of  the  organization  to  another  part,  and  to  the  condi¬ 
tions  of  life  and  of  one  organic  being  to  another  being, 
been  perfected?  We  see  these  beautiful  co-adaptations 
most  plainly  in  the  woodpecker  and  the  mistletoe;  and  only 
a  little  less  plainly  in  the  humblest  parasite  which  clings  to 
the  hairs  of  a  quadruped  or  feathers  of  a  bird;  in  the 
structure  of  the  beetle  which  dives  through  the  water;  in 
the  plumed  seed  which  is  wafted  by  the  gentlest  breeze;  in 


55 


STRUGGLE  FOR  EXISTENCE. 


short,  we  see  beautiful  adaptations  everywhere  and  in  every 
part  of  the  organic  world. 

Again,  it  may  be  asked,  how  is  it  that  varieties,  which  I 
have  called  incipient  species,  become  ultimately  converted 
into  good  and  distinct  species,  which  in  most  cases 
obviously  differ  from  each  other  far  more  than  do  the 
varieties  of  the  same  species?  How  do  those  groups  of 
species,  which  constitute  what  are  called  distinct  genera 
and  which  differ  from  each  other  more  than  do  the  species 
of  the  same  genus,  arise?  All  these  results,  as  we  shall 
more  fully  see  in  the  next  chapter,  follow  from  the  struggle 
for  life.  Owing  to  this  struggle,  variations,  however  slight 
and  from  whatever  cause  proceeding,  if  they  be  in  any 
degree  profitable  to  the  individuals  of  a  species,  in  their 
infinitely  complex  relations  to  other  organic  beings  and 
to  their  physical  conditions  of  life,  will  tend  to  the 
preservation  of  such  individuals,  and  will  generally  be 
inherited  by  the  offspring.  The  offspring,  also,  will 
thus  have  a  better  chance  of  surviving,  for,  of  the  many 
individuals  of  any  species  which  are  periodically  born, 
but  a  small  number  can  survive.  I  have  called  this 
|  principle,  by  which  each  slight  variation,  if  useful,  is 
1  preserved,  by  the  term  natural  selection,  in  order  to 
linark  its  relation  to  man's  power  of  selection.  But  the 
expression  often  used  by  Mr.  Herbert  Spencer,  of  the  Sur¬ 
vival  of  the  Fittest,  is  more  accurate,  and  is  sometimes 
*  equally  convenient.  We  have  seen  that  man  by  selection 
can  certainly  produce  great  results,  and  can  adapt  organic 
beings  to  his  own  uses,  through  the  accumulation  of  slight 
but  useful  variations,  given  to  him  by  the  hand  of  Nature. 
But  Natural  Selection,  we  shall  hereafter  see,  is  a  power 
incessantly  ready  for  action,  and  is  as  immeasurably  superior 
to  man's  feeble  efforts  as  the  works  of  Nature  are  to  those 
of  Art. 

We  will  now  discuss  in  a  little  more  detail  the  struggle 
for  existence.  In  my  future  work  this  subject  will  be 
treated,  as  it  well  deserves,  at  greater  length.  The  elder 
De  Candolle  and  Lyell  have  largely  and  philosophically 
shown  that  all  organic  beings  are  exposed  to  severe  compe¬ 
tition.  In  regard  to  plants,  no  one  has  treated  this  sub¬ 
ject  with  more  spirit  and  ability  than  W.  Herbert,  Dean 
of  Manchester,  evidently  the  result  of  his  great  horticul- 


STRUGGLE  FOR  EXISTENCE. 


59 


tural  knowledge.  Nothing  is  easier  than  to  admit  in 
words  the  truth  of  the  universal  struggle  for  life‘s  or  nrPre 
difficult — at  least  I  found  it  so — than  constantly  to  b&B’ 
this  conclusion  in  mind.  Yet  unless  it  be  thoroughly  en-\ 
grained  in  the  mind,  the  whole  economy  of  nature,  with 
every  fact  on  distribution,  rarity,  abundance,  extinction, 
and  variation,  will  be  dimly  seen  or  quite  misunderstood. 
We  behold  the  face  of  nature  bright  with  gladness,  we 
often  see  superabundance  of  food;  we  do  not  see  or  we 
forget  that  the  birds  which  are  idly  singing  round  us 
mostly  live  on  insects  or  seeds,  and  are  thus  constantly 
destroying  life;  or  we  forget  how  largely  these  songsters, 
or  their  eggs,  or  their  nestlings,  are  destroyed  by  birds  and 
beasts  of  prey;  we  do  not  always  bear  in  mind,  that, 
though  food  may  be  now  superabundant,  it  is  not  so  at  all 
seasons  of  each  recurring  year. 

THE  TERM,  STRUGGLE  FOR  EXISTENCE,  USED  IH  A  LARGE 

SEHSE. 

I  should  premise  that  I  use  this  term  in  a  large  and 
metaphorical  sense,  including  dependence  of  one  being  on 
another,  and  including  (which  is  more  important)  not 
only  the  life  of  the  individual,  but  success  in  leaving  prog¬ 
eny.  Two  canine  animals,  in.  a  time  of  dearth,  may  be 
truly  said  to  struggle  with  each  other  which  shall  get  food 
and  live.  But  a  plant  on  the  edge  of  a  desert  is  said  to 
struggle  for  life  against  the  drought,  though  more  prop¬ 
erly  it  should  be  said  to  be  dependent  on  the  moisture.  A 
plant  which  annually  produces  a  thousand  seeds,  of  which 
only  one  of  an  average  comes  to  maturity,  may  be  more 
truly  said  to  struggle  with  the  plants  of  the  same  and  other 
kinds  which  already  clothe  the  ground.  The  mistletoe  is 
dependent  on  the  apple  and  a  few  other  trees,  but  can 
only  in  a  far-fetched  sense  be  said  to  struggle  with  these 
trees,  for,  if  too  many  of  these  parasites  grow  on  the  same 
tree,  it  languishes  and  dies.  But  several  seedling  mistle¬ 
toes,  growing  close  together  on  the  same  branch,  may  more 
truly  be  said  to  struggle  with  each  other.  As  the  mistle¬ 
toe  is  disseminated  by  birds,  its  existence  depends  on  them; 
and  it  may  metaphorically  be  said  to  struggle  with  other 
fruit-bearing  plants,  in  tempting  the  birds  to  devour 


CO  GEOMETRICAL  RATIO  OF  INCREASE. 

thus  disseminate  its  seeds.  In  these  several  senses,  which 
pass  into  each  other,  I  use  for  convenience  sake  the  gen¬ 
eral  term  of  Struggle  for  Existence. 

GEOMETRICAL  RATIO  OF  INCREASE. 

—  A  struggle  for  existence  inevitably  follows  from  the  high 
rate  at  which  all  organic  beings  tend  to  increase.  Every 
being,  which  during  its  natural  lifetime  produces  several 
eggs  or  seeds,  must  suffer  destruction  during  some  period 
of  its  life,  and  during  some  season  or  occasional  year, 
otherwise,  on  the  principle  of  geometrical  increase,  its 
numbers  would  quickly  become  so  inordinately  great  that 
no  country  could  support  the  product.  Hence,  as  more 
individuals  are  produced  than  can  possibly  survive,  there 
must  in  every  case  be  a  struggle  for  existence,  either  one  in¬ 
dividual  with  another  of  the  same  species,  or  with  the 
individuals  of  distinct  species,  or  with  the  physical  con¬ 
ditions  of  life.  It  is  the  doctrine  of  Malthus  applied  with 
manifold  force  to  the  whole  animal  and  vegetable  king¬ 
doms;  for  in  this  case  there  can  be  no  artificial  increase  of 
food,  and  no  prudential  restraint  from  marriage.  Although 
some  species  may  be  now  increasing,  more  or  less  rapidly, 
in  numbers,  all  can  not  do  so,  for  the  world  would  not  hold 
them. 

There  is  no  exception  to  the  rule  that  every  organic 
being  naturally  increases  at  so  high  a  rate,  that,  if  not 
destroyed,  the  earth  would  soon  be  covered  by  the  progeny 
of  a  single  pair.  Even  slow- breeding  man  has  doubled  in 
twenty-five  years,  and  at  this  rate,  in  less  than  a  thousand 
years,  there  would  literally  not  be  standing-room  for  his 
progeny.  Linnaeus  has  calculated  that  if  an  annual  plant 
produced  only  two  seeds — and  there  is  no  plant  so  unpro¬ 
ductive  as  this — and  their  seedlings  next  year  produced 
two,  and  so  on,  then  in  twenty  years  there  would  be  a 
million  plants.  The  elephant  is  reckoned  the  slowest 
breeder  of  all  known  animals,  and  I  have  taken  some  pains  to 
estimate  its  probable  minimum  rate  of  natural  increase;  it 
will  be  safest  to  assume  that  it  begins  breeding  when  thirty 
years  old,  and  goes  on  breeding  till  ninety  years  old, 
bringing  forth  six  young  in  the  interval,  and  surviving  till 
one  hundred  years  old;  if  this  be  so,  after  a  period  of  from 


GEOMETRICAL  RATIO  OF  INCREASE.  61 

740  to  750  years  there  would  be  nearly  nineteen  million 
elephants  alive  descended  from  the  first  pair. 

But  we  have  better  evidence  on  this  subject  than  mere 
theoretical  calculations,  namely,  the  numerous  recorded 
cases  of  the  astonishingly  rapid  increase  of  various  animals 
in  a  state  of  nature,  when  circumstances  have  been  favor 
able  to  them  during  two  or  three  following  seasons.  Still 
more  striking  is  the  evidence  from  our  domestic  animals  of 
many  kinds  which  have  run  wild  in  several  parts  of  the 
world;  if  the  statements  of  the  rate  of  increase  of  slow- 
breeding  cattle  and  horses  in  South  America,  and  latterly 
in  Australia,  had  not  been  well  authenticated,  they  would 
have  been  incredible.  So  it  is  with  plants;  cases  could  be 
given  of  introduced  plants  which  have  become  common 
throughout  whole  islands  in  a  period  of  less  than  ten  years. 
Several  of  the  plants,  such  as  the  cardoon  and  a  tall  thistle, 
which  are  now  the  commonest  over  the  wide  plains  of  La 
Plata,  clothing  square  leagues  of  surface  almost  to  the  ex¬ 
clusion  of  every  other  plant,  have  been  introduced  from 
Europe;  and  there  are  plants  which  now  range  in  India,  as 
I  hear  from  Dr.  Falconer,  from  Cape  Comorin  to  the 
Himalaya,  which  have  been  inported  from  America  since 
its  discovery.  In  such  cases,  and  endless  others,  could  be 
given,  no  one  supposes,  that  the  fertility  of  the  animator 
plants  has  been  suddenly  and  temporarily  increased  in  any 
sensible  degree.  The  obvious  explanation  is  that  the  con¬ 
ditions  of  life  have  been  highly  favorable,  and  that  there 
has  consequently  been  less  destruction  of  the  old  and 
young  and  that  nearly  all  the  young  have  been  enabled  to 
breed.  Their  geometrical  ratio  of  increase,  the  result  of 
which  never  fails  to  be  surprising,  simply  explains  their 
extraordinarily  and  rapid  increase  and  wide  diffusion  in  their 
new  homes. 

In  a  state  of  nature  almost  every  full-grown  plant  an¬ 
nually  produces  seed,  and  among  animals  there  are  very 
few  which  do  not  annually  pair.  Hence  we  may  confi¬ 
dently  assert  that  all  plants  and  animals  are  tending  to  in¬ 
crease  at  a  geometrical  ratio — that  all  would  rapidly  stock 
every  station  in  which  they  could  anyhow  exist-r-and  that 
this  geometrical  tendency  to  increase  must  be  checked  by 
destruction  at  some  period  of  life.  Our  familiarity  with 
the  larger  domestic  animals  tends,,  I  think,  to  mislead  us; 


62 


GEOMETRICAL  RATIO  OF  INCREASE. 


we  see  no  great  destruction  falling  on  them,  but  we  do  not 
keep  in  mind  that  thousands  are  annually  slaughtered  for 
food,  and  that  in  a  state  of  nature  an  equal  number  would 
have  somehow  to  be  disposed  of. 

The  only  difference  between  organisms  which  annually 
produce  eggs  or  seeds  by  the  thousand,  and  those  which 
produce  extremely  few,  is,  that  the  slow  breeders  would  re¬ 
quire  a  few  more  years  to  people,  under  favorable  condi¬ 
tions,  a  whole  district,  let  it  be  ever  so  large.  The  condor 
lays  a  couple  of  eggs  and  the  ostrich  a  score,  and  yet  in  the 
same  country  the  condor  may  be  the  more  numerous  of  the 
two.  The  Fulmar  petrel  lays  but  one  egg,  yet  it  is  be¬ 
lieved  to  be  the  most  numerous  bird  in  the  world.  One 
fly  deposits  hundreds  of  eggs,  and  another,  like  the  hippo- 
bosca,  a  single  one.  But  this  difference  does  not  determine 
how  many  individuals  of  the  two  species  can  be  supported 
in  a  district.  A  large  number  of  eggs  is  of  some  im¬ 
portance  to  those  species  which  depend  on  a  fluctuating 
amount  of  food,  for  it  allows  them  rapidly  to  increase  in 
number.  But  the  real  importance  of  a  large  number  of 
eggs  or  seeds  is  to  make  up  for  much  destruction  at  some 
period  of  life;  and  this  period  in  the  great  majority  of 
cases  is  an  early  one.  If  an  animal  can  in  any  way  protect 
its  own  eggs  or  young,  a  small  number  may  be  produced, 
and  yet  the  average  stock  be  fully  kept  up;  but  if  many 
eggs  or  young  are  destroyed,  many  must  be  produced  or 
the  species  will  become  extinct.  It  would  suffice  to  keep 
up  the  full  number  of  a  tree,  which  lived  on  an  average 
for  a  thousand  years,  if  a  single  seed  were  produced  once 
in  a  thousand  years,  supposing  that  this  seed  were  never 
destroyed  and  could  be  insured  to  germinate  in  a  fitting 
place;  so  that,  in  all  cases,  the  average  number  of  any  an¬ 
imal  or  plant  depends  only  indirectly  on  the  number  of  its 
eggs  or  seeds. 

In  looking  at  Nature,  it  is  most  necessary  to  keep  the 
foregoing  considerations  always  in  mind — never  to  forget 
that  every  single  organic  being  may  be  said  to  be  striving 
to  the  utmost  to  increase  in  numbers;  that  each  lives  by  a 
struggle  at  some  period  of  its  life;  that  heavy  destruction 
inevitably  falls  either  on  the  young  or  old  during  each  gen¬ 
eration  or  at  recurrent  intervals.  Lighten  any  check,  mit¬ 
igate  the  destruction  ever  so  little,  and  the  number  of  the . 
species  will  almost  instantaneously  increase  to  any  amount 


NATURE  OF  THE  CHECKS  TO  INCREASE.  [t 
NATURE  OF  THE  CHECKS  TO  INCREASE. 

The  causes  which  check  the  natural  tendency  of  each 
species  to  increase  are  most  obscure.  Look  at  the  most 
vigorous  species;  by  as  much  as  it  swarms  in  numbers,  by 
so  much  will  it  tend  to  increase  still  further.  We  know 
not  exactly  what  the  checks  are  even  in  a  single  instance. 
Nor  will  this  surprise  any  one  who  reflects  how  ignorant 
we  are  on  this  head,  even  in  regard  to  mankind,  although 
so  incomparably  better  known  than  any  other  animal. 
This  subject  of  the  checks  to  increase  has  been  ably  treated 
by  several  authors,  and  I  hope  in  a  future  work  to  discuss 
it  at  considerable  length,  more  especially  in  regard  to  the 
feral  animals  of  South  America.  Here  I  will  make  only  a 
few  remarks,  just  to  recall  to  the  reader’s  mind  some*of  the 
chief  points.  Eggs  or  very  young  animals  seem  generally 
to  suffer  most,  but  this  is  not  invariably  the  case.  With 
plants  there  is  a  vast  destruction  of  seeds,  but  from  some 
observations  which  I  have  made  it  appears  that  the  seed¬ 
lings  suffer  most  from  germinating  in  ground  already 
thickly  stocked  with  other  plants.  Seedlings,  also,  are 
destroyed  in  vast  numbers  by  various  enemies;  for  instance, 
on  a  piece  of  ground  three  feet  long  and  two  wide,  dug  and 
cleared,  and  where  there  could  be  no  choking  from  other 
plants,  I  marked  all  the  seedlings  of  our  native  weeds  as 
they  came  up,  and  out  of  357  no  less  than  295  were  de¬ 
stroyed,  chiefly  by  slugs  and  insects.  If  turf  which  has 
long  been  mown,  and  the  case  would  be  the  same  with  turf 
closely  browsed  by  quadrupeds,  be  let  to  grow,  the  more 
vigorous  plants  gradually  kill  the  less  vigorous,  though 
fully  grown  plants;  thus  out  of  twenty  species  grown  on  a 
little  plot  of  mown  turf  (three  feet  by  four)  nine  species 
perished,  from  the  other  species  being  allowed  to  grow  up 
freely. 

The  amount  of  food  for  each  species,  of  course,  gives 
the  extreme  limit  to  which  each  can  increase;  but  very  fre¬ 
quently  it  is  not  the  obtaining  food,  but  the  serving  as  prey 
to  other  animals,  which  determines  the  average  number  of 
a  species.  Thus,  there  seems  to  be  little  doubt  that  the 
stock  of  partridges,  grouse  and  hares  on  any  large  estate 
depends  chiefly  on  the  destruction  of  vermin.  If  not  one 
head  of  game  were  shot  during  the  next  twenty  years  in 


£ 


NATURE  OF  THE  CHECKS  To  INCREASE. 


England,  and,  at  the  same  time,  if  no  vermin  were  de- 
stroyed,  there  would,  in  all  probability,  be  less  game  than 
at  present,  although  hundreds  of  thousands  of  game 
animals  are  now  annually  shot.  On  the  other  hand, 
in  some  cases,  as  with  the  elephant,  none  are  destroyed  by 
beasts  of  prey;  for  even  the  tiger  in  India  most  rarely  dares 
to  attack  a  young  elephant  protected  by  its  dam. 

Climate  plays  an  important  part  in  determining  the 
average  numbers  of  a  species,  and  periodical  seasons  of  ex¬ 
treme  cold  or  drought  seem  to  be  the  most  effective  of  all 
k  checks.  I  estimated  (chiefly  from  the  the  greatly  reduced 
numbers  of  nests  in  the  spring)  that  the  winter  of  1854-5 
destroyed  four-fifths  of  the  birds  in  my  own  grounds;  and 
this  is  a  tremendous  destruction,  when  we  remember  that 
ten  per  cent,  is  an  extraordinarily  severe  mortality  from 
epidemics  with  man.  The  action  of  climate  seems  at  first 
sight  to  be  quite  independent  of  the  struggle  for  existence; 


dmt  in  so  far  as  climate  chiefly  acts  in  reducing  food, 
jit  brings  on  the  most  severe  struggle  between  the  indi¬ 
viduals,  whether  of  the  same  or  of  distinct  species,  which 
subsist  on  the  same  kind  of  food.  Even  when  climate, 
for  instance,  extreme  cold,  acts  directly,  it  will  be  the  least 
vigorous  individuals,  or  those  which  have  got  least  food 
through  the  advancing  winter,  which  will  suffer  the  most. 
When  we  travel  from  south  to  north,  or  from  a  damp 
region  to  a  dry,  we  invariably  see  some  species  gradually 
getting  rarer  and  rarer,  and  finally  disappearing;  and  the 
change  of  climate  being  conspicious,  we  are  tempted  to 
attribute  the  whole  effect  to  its  direct  action.  But  this  is 
a  false  view;  we  forget  that  each  species,  even  where  it 
most  abounds,  is  constantly  suffering  enormous  destruc¬ 
tion  at  some  period  of  its  life,  from  enemies  or  from  com¬ 
petitors  for  the  same  place  and  food;  and  if  these  enemies 
or  competitors  be  in  the  least  degree  favored  by  any  slight 
change  of  climate,  they  will  increase  in  numbers;  and  as 
each  area  is  already  fully  stocked  with  inhabitants,  the 
other  species  must  decrease.  When  we  travel  southward 
and  see  a  species  decreasing  in  numbers,  we  may  feel  sure 
that  the  cause  lies  quite  as  much  in  other  species  being 
i  favored,  as  in  this  one  being  hurt.  So  it  is  when  we 
travel  northward,  but  in  a  somewhat  lesser  degree,  for 
the  number  of  species  of  all  kinds,  and,  therefore  of 


NATURE  OF  THE  CHECKS  TO  INCREASE. 


65 


competitors,  decreases  northward,  or  in  ascending  a  mount- 

Iain,  we  far  oftener  meet  with  stunted  forms,  due  to  the 
directly  injurious  action  of  climate,  than  we  do  in  proceed¬ 
ing  southward  or  in  descending  a  mountain.  When  we 
reach  the  Arctic  regions,  or  snow-capped  summits,  or  abso¬ 
lute  deserts,  the  struggle  for  life  is  almost  exclusively  with 
the  elements. 

I  That  climate  acts  in  main  part  indirectly  by  favoring 
other  species  we  clearly  see  in  the  prodigious  number  of} 
plants  which  in  our  gardens  can  perfectly  well  endure  our 
climate,  but  which  never  become  naturalized,  for  they 
cannot  compete  with  our  native  plants  nor  resist  destruc¬ 
tion  by  our  native  animals. 

When  a  species,  owing  to  highly  favorable  circumstances, 
increases  inordinately  in  numbers  in  a  small  tract,  epidem- 
ics — at  least,  this  seems  generally  to  occur  with  our  game 
animals — often  ensue;  and  here  we  have  a  limiting  check 
independent  of  the  struggle  for  life.  But  even  some  of 
these  so-called  epidemics  appear  to  be  due  to  parasitic 
worms,  which  have  from  some  cause,  possibly  in  part 
through  facility  of  diffusion  among  the  crowded  animals, 
but  disproportionally  favored:  and  here  comes  in  a  sort  of 
1  struggle  between  the  parasite  and  its  prey. 

On  the  other  hand,  in  many  cases,  a  large  stock  of  indi¬ 
viduals  of  the  same  species,  relatively  to  the  numbers  of  its 
.  enemies,  is  absolutely  necessary  for  its  preservation.  Thus 
we  can  easily  raise  plenty  of  corn  and  rape-seed,  etc.,  in 
our  fields,  because  the  seeds  are  in  great  excess  compared 
with  the  number  of  birds  which  feed  on  them;  nor  can  the 
birds,  though  having  a  superabundance  of  food  at  this  one 
season,  increase  in  number  proportionally  to  the  supply  of 
seed,  as  their  numbers  are  checked  during  the  winter;  but 
any  one  who  has  tried  knows  how  troublesome  it  is  to  get 
seed  from  a  few  wheat  or  other  such  plants  in  a  garden;  I 
have  in  this  case  lost  every  single  seed.  '  This  view  of  the 
necessity  of  a  large  stock  of  the  same  species  for  its  preser¬ 
vation,  explains,  I  believe,  some  singular  facts  in  nature 
such  as  that  of  very  rare  plants  being  sometimes  extremely 
abundant,  in  the  few  spots  where  they  do  exist;  and  that 
of  some  social  plants  being  social,  that  is  abounding  in 
individuals,  even  on  the  extreme  verge  of  their  range.  For 
in  such  cases,  we  may  believe,  that  a  plant  could  exist  only 


66 


STRUGGLE  FOR  EXISTENCE, 


where  the  conditions  of  its  life  were  so  favorable  that  many 
could  exist  together,  and  thus  save  the  species  from  utter 
destruction.  I  should  add  that  the  good  effects  of  inter¬ 
crossing,  and  the  ill  effects  of  close  interbreeding,  no 
doubt  come  into  play  in  many  of  these  cases;  but  I  will  not 
here  enlarge  on  this  subject. 

COMPLEX  RELATIONS  OF  ALL  ANIMALS  AND  PLANTS  TO 
EACH  OTHER  IN  THE  STRUGGLE  FOR  EXISTENCE. 

Many  cases  are  on  record  showing  how  complex  and  unex¬ 
pected  are  the  checks  and  relations  between  organic  beings, 
which  have  to  struggle  together  in  the  same  country.  I 
will  give  only  a  single  instance,  which,  though  a  simple 
one,  interested  me.  In  Staffordshire,  on  the  estate  of  a 
relation,  where  I  had  ample  means  of  investigation,  there 
was  a  large  and  extremely  barren  heath,  which  had  never 
been  touched  by  the  hand  of  man;  but  several  hundred 
acres  of  exactly  the  same  nature  had  been  inclosed  twenty- 
five  years  previously  and  planted  with  Scotch  fir.  The  change 
in  the  native  vegetation  of  the  planted  part  of  the  heath 
was  most  remarkable,  more  than  is  generally  seen  in  pass¬ 
ing  from  one  quite  different  soil  to  another:  not  only  the 
proportional  numbers  of  the  lieath-plants  were  wholly 
changed,  but  twelve  species  of  plants  (not  counting  grasses 
and  carices)  flourished  in  the  plantations,  which  could  not 
be  found  on  the  heath.  The  effect  on  the  insects  must 
have  been  still  greater,  for  six  insectivorous  birds  were  very 
common  in  the  plantations,  which  were  not  to  be  seen  on 
the  heath;  and  the  heath  was  frequented  by  two  or  three 
distinct  insectivorous  birds.  Here  we  see  how  potent  has 
been  the  effect  of  the  introduction  of  a  single  tree,  nothing 
whatever  else  having  been  done,  with  the  exception  of  the 
land  having  been  inclosed,  so  that  cattle  could  not  enter. 
But  how  important  an  element  inclosure  is,  I  plainly  saw 
near  Farnham,  in  Surrey.  Here  there  are  extensive  heaths, 
with  a  few  clumps  of  old  Scotch  firs  on  the  distant  hill¬ 
tops:  within  the  last  ten  years  large  spaces  have  been 
inclosed,  and  self-sown  firs  are  now  springing  up  in  multi¬ 
tudes,  so  close  together  that  all  cannot  live. .  When  I 
ascertained  that  these  young  trees  had  not  been  sown  or 
planted  I  was  so  much  surprised  at  their  numbers  that  I 


STRUGGLE  FOR  EXISTENCE. 


67 


went  to  several  points  of  view,  whence  I  could  examine 
hundreds  of  acres  of  the  uninclosed  heath,  and  literally  I 
could  not  see  a  single  Scotch  fir,  except  the  old  planted 
clumps.  But  on  looking  closely  between  the  stems  of  the 
heath,  I  found  a  multitude  of  seedlings  and  little  trees 
which  had  been  perpetually  browsed  down  by  the  cattle. 
In  one  square  yard,  at  a  point  some  hundred  yards  distant 
from  one  of  the  old  clumps,  I  counted  thirty-two  little 
trees;  and  one  of  them,  with  twenty-six  rings  of  growth, 
had,  during  many  years  tried  to  raise  its  head  above  the 
stems  of  the  heath,  and  had  failed.  No  wonder  that,  as 
soon  as  the  land  was  inclosed,  it  became  thickly  clothed 
with  vigorously  growing  young  firs.  Yet  the  heath  was  so 
extremely  barren  and  so  extensive  that  no  one  would  ever 
have  imagined  that  cattle  would  have  so  closely  and  effec¬ 
tually  searched  it  for  food. 

Here  we  see  that  cattle  absolutely  determine  the 
existence  of  the  Scotch  fir;  but  in  several  parts  of  the 
world  insects  determine  the  existence  of  cattle.  Perhaps 
Paraguay  offers  the  most  curious  instance  of  this;  for  here 
neither  cattle  nor  horses  nor  dogs  have  ever  run  wild, 
though  they  swarm  southward  and  northward  in  a  feral 
state;  and  Azara  and  Rengger  have  shown  that  this  is 
caused  by  the  greater  number  in  Paraguay  of  a  certain  fly, 
which  lays  its  eggs  in  the  navels  of  these  animals  when 
first  born.  The  increase  of  these  flies,  numerous  as  they 
are,  must  be  habitually  checked  by  some  means,  probably 
by  other  parasitic  insects.  Hence,  if  certain  insectivorous 
birds  were  to  decrease  in  Paraguay,  the  parasitic  insects 
would  probably  increase;  and  this  would  lessen  the  num¬ 
ber  of  the  navel-frequenting  flies — then  cattle  and  horses 
would  become  feral,  and  this  would  certainly  greatly  alter 
(as  indeed  I  have  observed  in  parts  of  South  America)  the 
vegetation:  this  again  would  largely  affect  the  insects;  and 
this,  as  we  have  just  seen  in  Staffordshire,  the  insectivor¬ 
ous  birds,  and  so  onward  in  ever-increasing  circles  of  com¬ 
plexity.  Not  that  under  nature  the  relations  will  ever  be 
as  simple  as  this.  Battle  within  battle  must  be  continually 
recurring  with  varying  success;  and  yet  in  the  long-run 
the  forces  are  so  nicely  balanced  that  the  face  of  nature 
remains  for  long  periods  of  time  uniform,  though  assuredly 
the  merest  trifle  would  give  the  victory  to  one  organic 


68 


STRUGGLE  FOR  EXISTENCE. 


being  over  another.  Nevertheless,  so  profound  is  our 
ignorance,  and  so  high  our  presumption,  that  we  marvel 
when  we  hear  of  the  extinction  of  an  organic  being;  and 
as  we  do  not  see  the  cause,  we  invoke  cataclysms  to  deso¬ 
late  the  world,  or  invent  laws  on  the  duration  of  the  forms 
/of  life! 

f  I  am  tempted  to  give  one  more  instance  showing  how 
'  plants  and  animals,  remote  in  the  scale  of  nature,  are 
bound  together  by  a  web  of  complex  relations.  I  shall 
,  hereafter  have  occasion  to  show  that  the  exotic  Lobelia 
folgens  is  never  visited  in  my  garden  by  insects,  and  con¬ 
sequently,  from  its  peculiar  structure,  never  sets  a  seed. 
Nearly  all  our  orchidaceous  plants  absolutely  require  the 
visits  of  insects  to  remove  their  pollen-masses  and  thus  to 
fertilize  them.  I  find  from  experiments  that  Bumble-bees 
are  almost  indispensable  to  the  fertilization  of  the  hearts¬ 
ease  (Yiolo  tricolor),  for  other  bees  do  not  visit  this  flower. 
I  have  also  found  that  the  visits  of  bees  are  necessary  for  the 
fertilization  of  some  kinds  of  clover;  for  instance  twenty 
heads  of  Dutch  clover  (Trifolium  repens)  yielded  2,290 
seeds,  but  twenty  other  heads,  protected  from  bees,  produced 
not  one.  Again,  100  heads  of  red  clover  (T.  pratense) 
produced  2,700  seeds,  but  the  same  number  of  protected 
heads  produced  not  a  single  seed.  Humble-bees  alone 
visit  red  clover,  as  other  bees  cannot  reach  the  nectar.  It 
has  been  suggested  that  moths  may  fertilize  the  clovers; 
but  I  doubt  whether  they  could  do  so  in  the  case  of  the 
red  clover,  from  their  weight  not  being  sufficient  to  depress 
the  wing  petals.  Hence  we  may  infer  as  highly  probable 
that,  if  the  whole  genus  of  humble-bees  became  extinct  or 
very  rare  in  England,  the  heartsease  and  red  clover  would 
become  very  rare,  or  wholly  disappear.  The  number  of 
humble-bees  in  any  district  depends  in  a  great  measure 
upon  the  number  of  field-mice,  which  destroy  their  combs 
and  nests;  and  Colonel  Newman,  who  has  long  attended  to 
the  habits  of  humble-bees,  believes  that  “more  than  two- 
thirds  of  them  are  thus  destroyed  all  over  England.” 
Now  the  number  of  mice  is  largely  dependent,  as  every 
one  knows,  on  the  number  of  cats;  and  Colonel  Newman 
says,  “  Near  villages  and  small  towns  I  have  found  the 
nests  of  humble-bees  more  numerous  than  elsewhere, which 
I  attribute  to  the  number  of  cats  that  destroy  the  mice.” 


3TTUGGLE  FOB  EXISTENCE. 


69 


Hence  it  is  quite  Credible  that  the  presence  of  a  feline 
animal  in  large  numbers  in  a  district  might  determine, 
through  the  intervention  first  of  mice  and  then  of  bees, 
the  frequency  of  certain  flowers  in  that  district! 

In  the  case  of  every  species,  many  different  checks,  act¬ 
ing  at  different  periods  of  life,  and  during  different  seasons 
or  years,  probably  come  into  play;  some  one  check  or  some 
few  being  generally  the  most  potent;  but  all  will  concur  in 
determining  the  average  number,  or  even  the  existence  of 
the  species.  In  some  cases  it  can  be  shown  that  widely 
different  checks  act  on  the  same  species  in  different  dis¬ 
tricts.  When  we  look  at  the  plants  and  bushes  clothing 
an  entangled  bank,  we  are  tempted  to  attribute  their  pro¬ 
portional  numbers  and  kinds  to  what  we  call  chance.  But 
how  false  a  view  is  this!  Every  one  has  heard  that  when 
an  American  forest  is  cut  down,  a  very  different  vegetation 
springs  up;  but  it  has  been  observed  that  ancient  Indian 
ruins  in  the  Southern  United  States,  which  must  formerly 
have  been  cleared  of  trees,  now  display  the  same  beautiful 
diversity  and  proportion  of  kinds  as  in  the  surrounding 
virgin  forests.  What  a  struggle  must  have  gone  on  during 
long  centuries  between  the  several  kinds  of  trees,  each 
annually  scattering  its  seeds  by  the  thousand;  what  war 
between  insect  and  insect — between  insects,  snails  and 
other  animals  with  birds  and  beasts  of  prey — all  striving  to 
increase,  all  feeding  on  each  other,  or  on  the  trees,  their 
seeds  and  seedlings,  or  on  the  other  plants  which  first 
clothed  the  ground  and  thus  checked  the  growth  of  the 
trees.  Throw  up  a  handful  of  feathers  and  all  fall  to  the 
ground  according  to  definite  laws;  but  how  simple  is  the 
problem  where  each  shall  fall  compared  to  that  of  the 
action  and  reaction  of  the  innumerable  plants  and  animals 
which  have  determined,  in  the  course  of  centuries,  the 
proportional  numbers  and  kinds  of  trees  now  growing  on 
the  old  Indian  ruins! 

The  dependency  of  one  organic  being  on  another,  as  of  a 
parasite  on  its  prey,  lies  generally  between  beings  remote 
in  the  scale  of  nature.  This  is  likewise  sometimes  the 
case  with  those  which  may  be  strictly  said  to  struggle  with 
each  other  for  existence,  as  in  the  case  of  locusts  and  grass- 
feeding  quadrupeds.  But  the  struggle  will  almost  invari¬ 
ably  be  most  severe  between  the  individuals  of  the  same 


70 


STRUGGLE  FOR  EXISTENCE. 


Bpecies,  for  they  frequent  the  same  districts,  require  the 
same  food,  and  are  exposed  to  the  same  dangers.  In  the 
case  of  varieties  of  the  same  species,  the  struggle  will 
generally  be  almost  equally  severe,  and  we  sometimes  see 
the  contest  soon  decided:  for  instance,  if  several  varieties 
of  wheat  be  sown  together  and  the  mixed  seed  be  resown, 
some  of  the  varieties  which  best  suit  the  soil  or  climate, 
or  are  naturally  the  most  fertile,  will  beat  the  others 
and  so  yield  more  seed,  and  will  consequently  in  a 
few  years  supplant  the  other  varieties.  To  keep  up  a 
mixed  stock  of  even  such  extremely  close  varieties  as 
the  variously  colored  sweet  peas,  they  must  be  each 
year  harvested  separately,  and  the  seed  then  mixed 
in  due  proportion,  otherwise  the  weaker  kinds  will 
steadily  decrease  in  number  and  disappear.  So  again 
with  the  varieties  of  sheep;  it  has  been  asserted  that  certain 
mountain  varieties  will  starve  out  other  mountain  varieties, 
so  that  they  cannot  be  kept  together.  The  same  result 
has  followed  from  keeping  together  different  varieties  of 
the  medicinal  leech.  It  may  even  be  doubted  whether  the 
varieties  of  any  of  our  domestic  plants  or  animals  have  so 
exactly  the  same  strength,  habits,  and  constitution,  that 
the  original  proportions  of  a  mixed  stock  (crossing  being 
prevented)  could  be  kept  up  for  half-a-dozen  generations, 
if  they  were  allowed  to  struggle  together,  in  the  same  mari¬ 
ner  as  beings  in  a  state  of  nature,  and  if  the  seed  or  young 
were  not  annually  preserved  in  due  proportion 

STRUGGLE  FOR  LIFE  MOST  SEVERE  BETWEEN-  INDIVIDUALS 
AND  VARIETIES  OF  THE  SAME  SPECIES. 

As  the  species  of  the  same  genus  usually  have,  though 
by  no  means  invariably,  much  similarity  in  habits  and 
constitution,  and  always  in  structure,  the  struggle  will 
generally  be  more  severe  between  them,  if  they  come  into 
'  competition  with  each  other,  than  between  the  species 
of  distinct  genera.  We  see  this  in  the  recent  extension 
over  parts  of  the  United  States  of  one  species  of  swallow 
having  caused  the  decrease  of  another  species.  The  recent 
increase  of  the  missel-thrush  in  parts  of  Scotland  has  caused 
the  decrease  of  the  song-thrush.  How  frequently  we  hear 
of  one  species  of  rat  taking  the  place  of  another  species 


„  STRUGGLE  FOR  EXISTENCE. 


n 


under  the  most  different  climates!  In  Russia  the  small 
Asiatic  cockroach  has  everywhere  driven  before  it  its  great 
congener.  In  Australia  the  imported  hive-bee  is  rapidly 
exterminating  the  small,  stingless  native  bee.  One  species 
of  charlock  has  been  known  to  supplant  another  species; 
and  so  in  other  cases.  We  can  dimly  see  why  the  com¬ 
petition  should  be  most  severe  between  allied  forms,  which 
fill  nearly  the  same  place  in  the  economy  of  nature;  but 
probably  in  no  one  case  could  we  precisely  say  why  one 
species  has  been  victorious  over  another  in  the  great  battle 
of  life. 

A  corollary  of  the  highest  importance  may  be  deduced 
from  the  foregoing  remarks,  namely,  that  the  structure  of 
every  organic  being  is  related,  in  the  most  essential  yet 
often  hidden  manner,  to  that  of  all  the  other  organic 
beings,  with  which  it  comes  into  competition  for  food  or 
residence,  or  from  which  it  has  to  escape,  or  on  which  it 
preys.  This  is  obvious  in  the  structure  of  the  teeth  and 
talons  of  the  tiger;  and  in  that  of  the  legs  and  claws  of  the 
parasite  which  clings  to  the  hair  on  the  tiger’s  body.  But 
in  the  beautifully  plumed  seed  of  the  dandelion,  and  in 
the  flattened  and  fringed  legs  of  the  water-beetle,  the  re¬ 
lation  seems  at  first  confined  to  the  elements  of  air  and 
water.  Yet  the  advantage  of  the  plumed  seeds  no  doubt 
stands  in  the  closest  relation  to  the  land  being  already 
thickly  clothed  with  other  plants,  so  that  the  seeds  may 
be  widely  distributed  and  fall  on  unoccupied  ground.  In 
the  water-beetle,  the  structure  of  its  legs,  so  well  adapted 
for  diving,  allows  it  to  compete  with  other  aquatic  insects, 
to  hunt  for  its  own  prey,  and  to  escape  serving  as  prey  to 
other  animals. 

The  store  of  nutriment  laid  up  within  the  seeds  of  many 
plants  seems  at  first  sight  to  have  no  sort  of  relation  to 
other  plants.  But  from  the  strong  growth  of  young  plants 
produced  from  such  seeds,  as  peas  and  beans,  when  sown 
m  the  midst  of  long  grass,  it  may  be  suspected  that  the 
chief  use  of  the  nutriment  in  the  seed  is  to  favor  the  growth 
of  the  seedlings,  while  struggling  with  other  plants  growing 
vigorously  all  around. 

Look  at  a  plant  in  the  midst  of  its  range!  Why  does  it 
not  double  or  quadruple  its  numbers?  We  know  that  it 
can  perfectly  well  withstand  a  little  more  heat  or  cold. 


STRUGGLE  FOR  EXISTENCE. 


72 

H  ' 

dampness  or  dryness,  for  elsewhere  it  ranges  into  slightly 
hotter  or  colder,  damper  or  drier  districts.  In  this  case  we 
can  clearly  see  that  if  we  wish  in  imagination  to  give  the 
plant  the  power  of  increasing  in  numbers,  we  should  have 
to  give  it  some  advantage  over  its  competitors,  or  over  the 
animals  which  prey  on  it.  On  the  confines  of  its  geo¬ 
graphical  range,  a  change  of  constitution  with  respect  to 
climate  would  clearly  be  an  advantage  to  our  plant;  but  we 
have  reason  to  believe  that  only  a  few  plants  or  animals 
range  so  far,  that  they  are  destroyed  exclusively  by  the 
rigor  of  the  climate.  Not  until  we  reach  the  extreme  con¬ 
fines  of  life,  in  the  Arctic  regions  or  on  the  borders  of  an 
utter  desert,  will  competition  cease.  The  land  may  be  ex¬ 
tremely  cold  or  dry,  yet  there  will  be  competition  between 
some  few  species,  or  between  the  individuals  of  the  same 
species,  for  the  warmest  or  dampest  spots. 

Hence  we  can  see  that  when  a  plant  or  animal  is  placed 
in  a  new  country,  among  new  competitors,  the  conditions 
of  its  life  will  generally  be  changed  in  an  essential  manner, 
although  the  climate  may  be  exactly  the  same  as  in  its 
former  home.  If  its  average  numbers  are  to  increase  in 
its  new  home,  we  should  have  to  modify  it  in  a  different 
way  to  what  we  should  have  had  to  do  in  its  native 
country;  for  we  should  have  to  give  it  some  advantage 
over  a  different  set  of  competitors  or  enemies. 

It  is  good  thus  to  try  in  imagination  to  give  any  one  species 
an  advantage  over  another.  Probably  in  no  single  instance 
should  we  know  what  to  do.  This  ought  to  convince  us  of 
our  ignorance  on  the  mutual  relations  of  all  organic  beings; 
ji  conviction  as  necessary,  as  it  is  difficult  to  acquire.  All 
that  we  can  do  is  to  keep  steadily  in  mind  that  each  or¬ 
ganic  being  is  striving  to  increase  in  a  geometrical  ratio; 
that  each,  at  some  period  of  its  life,  during  some  season  of 
the  year,  during  each  generation,  or  at  intervals,  has  to 
struggle  for  life  and  to  suffer  great  destruction.  When  we 
reflect  on  this  struggle  we  may  console  ourselves  with  the 
full  belief  that  the  war  of  nature  is  not  incessant,  that  ho 
fear  is  felt,  that  death  is  generally  prompt,  and  that  the 
vigorous,  the  healthy  and  the  happy  survive  and  multiply. 


NATURAL  SELECTION. 


73 


CHAPTER  IV. 

NATURAL  SELECTION;  OR  THE  SURVIVAL  OF  THE  FITTEST. 

Natural  Selection — its  power  compared  witli  man’s  selection — its 
power  on  characters  of  trifling  importance — its  power  at  all  ages 
and  on  both  sexes — Sexual  Selection — On  the  generality  of  inter¬ 
crosses  between  individuals  of  the  same  species — Circumstances 
favorable  and  unfavorable  to  the  results  of  Natural  Selection, 
namely,  intercrossing,  isolation,  number  of  individuals — Slow 
action — Extinction  caused  by  Natural  Selection — Divergence  of 
Character,  related  to  the  diversity  of  inhabitants  of  any  small 
area  and  to  naturalization — Action  of  Natural  Selection,  through 
Divergence  of  Character  and  Extinction,  on  the  descendants 
from  a  common  parent — Explains  the  grouping  of  all  organic 
beings — Advance  in  organization — Low  forms  preserved — Con¬ 
vergence  of  character — Indefinite  multiplication  of  species — 
Summary. 

How  will  the  struggle  for  existence,  briefly  discussed  in 
the  last  chapter,  act  in  regard  to  variation?  Can  the  prin¬ 
ciple  of  selection,  which  we  have  seen  is  so  potent  in  the 
hands  of  man,  apply  under  pat  jura?  I  think  we  shall 
see  that  it  can  act  most  efficiently.  Let  the  endless 
number  of  sliglit  variations  and  individual  differences 
occurring  in  our  domestic  productions,  and,  in  a  lesser 
degree,  in  those  under  nature,  be  borne  in  mind;  as  well  as 
the  strength  of  the  hereditary  tendency.  Under  domesti¬ 
cation,  it  may  truly  be  said  that  the  whole  organization 
becomes  in  some  degree  plastic.  But  the  variability,  which 
we  almost  universally  meet  with  in  our  domestic  produc¬ 
tions  is  not  directly  produced,  as  Hooker  and  Asa  Gray 
have  well  remarked,  by  man;  he  can  neither  originate 
varieties  nor  prevent  their  occurrence;  he  can  only  pre¬ 
serve  and  accumulate  such  as  do  occur.  Unintentionally 
he  exposes  organic  beings  to  new  and  changing  conditions 
of  life,  and  variability  ensues;  but  similar  changes  of  con¬ 
ditions  might  and  do  occur  under  nature.  Let  it  also  be 


^  NATURAL  SELECTION \ 

borne  in  mind  how  infinitely  complex  and  close-fitting  are 
the  mutual  relations  of  all  organic  beings  to  each  other 
and  to  their  physical  conditions  of  life;  and  consequently 
what  infinitely  varied  diversities  of  structure  might  bo  of 
use  to  each  being  under  changing  conditions  of  life.  Can 
it  then  be  thought  improbable,  seeing  that  vanations 
useful  to  man  have  undoubtedly  occurred,  that  other 
variations  useful  in  some  way  to  each  being  in  the  gieat 
and  complex  battle  of  life,  should  occur  in  the  course  of 
many  successive  generations?  If  such  do  occur,  can  we 
doubt  (remembering  that  many  more  individuals  aie  bom 
than  can  possibly  survive)  that  individuals  having  any  ad- 
vantage,  however  slight,  over  others,  would  have  the  best 
chance  of  surviving  and  procreating  their  kind .  On  the 
other  hand,  we  may  feel  sure  that  any  variation  m  the  least 
degree  injurious  would  be  rigidly,  destroyed.  This  preser¬ 
vation  of  farm-able  individual  differences  and  variations, 
and  the  destruction  of  those  which  are  rajunpus,  I  ^ave 
called  Natural  Selection,  or  the  .Survival  of  the  fittest. 
Variations  neither  useful  nor  injurious  would  not  be  affected 
by  natural  selection,  and  would  be  left  either  a  fluctuati  g 
element,  as  perhaps  we  see  in  certain  polymorphic  sPeclc  > 
or  would  ultimately  become  fixed,  owing  to  the  nature  of 
the  organism  and  the  nature  of  the  conditions. 

Several  writers  have  misapprehended  or  objected  to  the 
term  Natural  Selection.  Some  have  even  imagined  that 
natural  selection  induces  variability,  whereas,  it  implies 
only  the  preservation  of  such  variations  as  arise  and  aie 
beneficial  to  the  being  under  its  conditions  of  life  No 
one  objects  to  agriculturists  speaking  of  the  potent  effects 
of  man’s  selection;  and  in  this  case  the  individual  differ¬ 
ences  given  by  nature,  which  man  for  some  object  selects 
must  of  necessity  first  occur.  Others  have,  objected,  that 
the  term  selection  implies  conscious  choice  in  the  animals 
which  become  modified;  and  it  has  even  been  urged  that, 
as  plants  have  no  volition,  natural  selection  is  not  applica¬ 
ble  to  them!  In  the  literal  sense  of  the  word,  no  doubt, 
natural  selection  is  a  false  term;  but  who  ever  objected  to 
chemists  speaking  of  the  elective  affinities  of  the  vanous 
elements?— and  yet  an  acid  cannot  strictly  be  said  to  elect 
the  base  with  which  it  in  preference  combines.  It  has 
been  said  that  I  speak  of  natural  selection  as  an  active 


NATURAL  SELECTION. 


75 


power  or  Deity;  but  who  objects  to  an  author  speaking  of 
the  attraction  of  gravity  as  ruling  the  movements  of  the 
planets?  Every  one  knows  what  is  meant  and  is  implied 
by  such  metaphorical  expressions;  and  they  are  almost 
necessary  for  brevity.  So  again  it  is  difficult  to  avoid  peN 
sonifying  the  word  Nature;  but  I  mean  by  nature,  only 
the  aggregate  action  and  product  of  many  natural  laws, 
and  by  laws  the  sequence  of  events  as  ascertained  by  us. 
With  a  little  familiarity  such  superficial  objections  will  be 
forgotten. 

We  shall  best  understand  the  probable  course  of  natural 
selection  by  taking  the  case  of  a  country  undergoing  some 
slight  physical  change,  for  instance,  of  climate.  The  pro¬ 
portional  numbers  of  its  inhabitants  will  almost  immedi¬ 
ately  undergo  a  change,  and  some  species  will  probably  be¬ 
come  extinct.  We  may  conclude,  from  what  we  have  seen 
of  the  intimate  and  complex  manner  in  which  the  inhabi¬ 
tants  of  each  country  are  bound  together,  that  any  change 
in  the  numerical  proportions  of  the  inhabitants,  independ¬ 
ently  of  the  change  of  climate  itself,  would  seriously  affect 
the  others.  If  the  country  were  open  on  its  borders,  new 
forms  would  certainly  immigrate,  and  this  would  likewise 
seriously  disturb  the  relations  of  some  of  the  former  inhab¬ 
itants.  Let  it  be  remembered  how  powerful  the  influence 
of  a  single  introduced  tree  or  mammal  has  been  shown  to 
be.  But  in  the  case  of  an  island,  or  of  a  country  partly 
surrounded  by  barriers,  into  which  new  and  better  adapted 
forms  could  not  freely  enter,  we  should  then  have  places  in 
the  economy  of  nature  which  would  assuredly  be  better  filled 
up  if  some  of  the  original  inhabitants  were  in  some  man¬ 
ner  modified;  for,  had  the  area  been  open  to  immigration, 
these  same  places  would  have  been  seized  on  by  intruders. 
In  such  cases,  slight  modifications,  which  in  any  way 
favored  the  individuals  of  any  species,  by  better  adapting 
them  to  their  altered  conditions,  would  tend  to  be  pre¬ 
served;  and  natural  selection  would  have  free  scope  for  the 
work  of  improvement. 

We  have  good  reason  to  believe,  as  shown  in  the  first 
chapter,  that  changes  in  the  conditions  of  life  give  a  ten¬ 
dency  to  increased  variability;  and  in  the  forgoing  cases 
the  conditions  have  changed,  and  this  would  manifestly  be 
favorable  to  natural  selection,  by  affording  a  better  chance 


76  NATURAL  SELECTION 

of  the  occurrence  of  profitable  variations.  Unless  such 
occur,  natural  selection  can  do  nothing.  Under  le 
term  of  "  variations,”  it  must  never  he  forgotten  that 
mere  individual  differences  are  included. .  .As  man 
can  produce  a  great  result  with  his  domestic  animals  and 
plants  by  adding  up  in  any  given  direction  individual  dif¬ 
ferences,  so  could  natural  selection,  but  far  more  easily 
from  having  incomparably  longer  time  for  action  JNor 
do  I  believe  that  any  great  physical  change,  as  of  climate, 
or  any  unusual  degree  of  isolation,  to  check  immigration,  is 
necessary  in  order  that  new  and  unoccupied  places  should 
be  left  for  natural  selection  to  fill  up  by  improving  some 
of  the  varying  inhabitants.  For  as  all  the  inhabitants  of 
each  country  are  struggling  together  with  nicely  balanced 
forces,  extremely  slight  modifications  m  the  structure  or 
habits  of  one  species  would  often  give  it  an  advantage  over 
others-  and  still  further  modifications  of  the  same  kind 
would  often  still  further  increase  the  advantage,  as  long  as 
the  species  continued  under  the  same  conditions  ot  me 
and  profited  by  similar  means  of  subsistence  and.  defence. 

^STo  country  can  be  named  in  which  all  the  native  inhab¬ 
itants  are  now  so  perfectly  adapted  to  each  other  and  to 
the  physical  conditions  under  which  they  live,  that  none 
of  them  could  be  still  better  adapted  or  improved;  for  in 
all  countries  the  natives  have  been  so  far  conquered  by 
naturalized  productions  that  they  have  allowed  some  for¬ 
eigners  to  take  firm  possession  of  the  land.  And  as  for¬ 
eigners  have  thus  in  every  country  beaten  some  of  the 
natives,  we  may  safely  conclude  that  the  natives  might 
have  been  modified  with  advantage,  so  as  to  have  better 

resisted  the  intruders.  ,  . 

As  man  can  produce,  and  certainly  has  produced,  a  great 
result  by  his  methodical  and  unconscious  means  of  selec¬ 
tion,  what  may  not  natural  selection  effect?  Man  can  act 
only  on  external  and  visible  characters;  Nature,  if  I  may 
be  allowed  to  personify  the  natural  preservation  or  survival; 
of  the  fittest,  cares  nothing  for.  appearances,  except  in  so 
far  as  they  are  useful  to  any  being.  She  can  act  on  every 
internal  organ,  on  every  shade  of  constitutional  difference 
on  the  whole  machinery  of  life.  Man  selects  only  for  his 
own  o-oocl ;  Nature  only  for  that  of  the  bein^  which  she 
tends.  Every  selected  character  is  fully  exercised  by  liei, 


NATURAL  SELECTION. 


77 


as  is  implied  by  the  fact  of  their  selection.  Man  keeps  the 
natives  of  many  climates  in  the  same  country.  He  seldom 
exercises  each  selected  character  in  some  peculiar  and  fit¬ 
ting  manner;  he  feeds  a  long  and  a  short-beaked  pigeon  on 
the  same  food;  he  does  not  exercise  a  long-backed  or  long- 
legged  quadruped  in  any  peculiar  manner;  he  exposes 
sheep  with  long  and  short  wool  to  the  same  climate;  does 
not  allow  the  most  vigorous  males  to  struggle  for  the 
females;  he  does  not  rigidly  destroy  all  inferior  animals, 
but  protects  during  each  varying  season,  as  far  as  lies  in 
his  power,  all  his  productions.  He  often  begins  his  selec¬ 
tion  bv  some  half-monstrous  form,  or  at  least  by  some  mod¬ 
ification  prominent  enough  to  catch  the  eye  or  to  be 
plainly  useful  to  him.  Under  nature^ the  slightest  differ¬ 
ences  of  structure  or  constitution  may  well  turn  the  nicely 
balanced  scale  in  the  struggle  for  life,  and  so  be  preserved. 
How  fleeting  are  the  wishes  and  efforts  of  man!  How 
short  his  time,  and  consequently  how  poor  will  be  his 
results,  compared  with  those  accumulated  by  Nature 
during  whole  geological  periods!  Can  we  wonder,  then, 
that  Nature’s  productions  should  be  far  “ truer”  in  char¬ 
acter  than  man’s  productions;  that  they  should  be  infinitely 
better  adapted  to  the  most  complex  conditions  of  life, 
and  should  plainly  bear  the  stamp  of  far  higher  workman¬ 
ship? 

It  may  metaphorically  be  said  that  natural  selection 
is  daily  and  hourly  scrutinizing,  throughout  the  world,  the 
slightest  variations;  rejecting  those  that  are  bad,  preserv-  j 
ing  and  adding  up  all  that  are  good;  silently  and  insen¬ 
sibly  working,  whenever  and  wherever  opportunity  offers , 
at  the  improvement  of  each  organic  being  in  relation  to  its 
organic  and  inorganic  conditions  of  life.  We  see  nothing 
of  these  slow  changes  in  progress,  until  the  hand  of  time 
has  marked  the  lapse  of  ages,  and  then  so  imperfect  is  our 
view  into  long-past  geological  ages  that  we  see  only  that 
the  forms  of  life  arq  now  different  from  what  they  formerly  j 
were. 

In  order  that  any  great  amount  of  modification  should 
be  effected  in  a  species,  a  variety,  when  once  formed 
must  again,  perhaps  after  a  long  interval  of  time, 
vary  or  present  individual  differences  of  the  same  favorable 
nature  as  before;  and  these  must  again  be  preserved,  and 


78 


NATURAL  SELECTION. 


so  onward,  step  by  step.  Seeing  that  individual  differences 
of  the  same  kind  perpetually  recur,  this  can  hardly  be  con¬ 
sidered  as  an  unwarrantable  assumption.  But  whether  it 
is  true,  we  can  judge  only  by  seeing  how  far  the  bypotlie- 
sis  accords  with  and  explains  the  general  phenomena  of 
nature.  On  the  other  hand,  the  ordinary  belief  that  the 
amount  of  possible  variation  is  a  strictly  limited  quantity, 

is  likewise  a  simple  assumption.  ,  * 

Although  natural  selection  can  act  only  through  and  for 
.the  good° of  each  being,  yet  characters  and  structures, 

\ which  we  are  apt  to  consider  as  of  very  trifling  importance, 
‘may  thus  be  acted  on.  When  we  see  leaf-eating  insects 
green,  and  bark-feeders  mottled-gray;  the  alpine  ptarmigan 
white  in  winter,  the  red  grouse  the  color  of  heathei,  we 
must  believe  that  these  tints  are  of  service  to  these  buds 
and  insec tr  in  preserving  them  from  danger.  Grouse,  if 
not  destroyed  at  some  period  of  their  lives,  would  lncieaso 
in  countless  numbers;  they  are  known  to  suffer  barge  y 
from  birds  of  prey;  and  hawks  are  guided  by  eyesight  to 
their  prey— so  much  so  that  on  parts  of  the  continent  per¬ 
sons  are  warned  not  to  keep  white  pigeons,  as  being  the 
most  liable  to  destruction.  Hence  natural  selection  mig  1 
/  be  effective  in  giving  the  proper  color  to  each  kind  ol 
'  grouse,  and  in  keeping  that  color  when  once  acquired 
true  and  constant.  Nor  ought  we  to  think  that  the  oc¬ 
casional  destruction  of  an  animal  of  any  particular  color 
would  produce  little  effect;  we  should  remember  how 
essential  it  is  in  a  flock  of  white  sheep  to  destroy  a  lamb 
with  the  faintest  trace  of  black.  We  have  seen  how  the 
color  of  hogs,  which  feed  on  the  “pamt-root  in  Virginia 
determines  whether  they  shall  live  or  die.  In  plants  the 
down  on  the  fruit  and  the  color  of  the  flesh  are  consideied 
by  botanists  as  characters  of  the  most  trifling  importance; 
vet  we  hear  from  an  excellent  horticulturist.  Downing, 
that  in  the  United  States  that  smooth-skinned  fruits  suffer 
far  more  from  a  beetle,  a  Curcuho,  than  those  with  down, 
that  purple  plums  suffer  far  more  from  a  certain  disease 
than  yellow  plums;  whereas  another  disease  attacks  yellow- 
fleshed  peaches  far  more  those  with  other  colored 
flesh.  If,  with  all  the  aids  of  art,  these  slight  differ¬ 
ences  make  a  great  difference  in  cultivating  the  several 
varieties,  assuredly,  in  a  state  of  nature,  where  the  trees 


NATURAL  SELECTION. 


79 


would  have  to  struggle  with  other  trees  and  with  a  host  of 
enemies,  such  differences  would  effectually  settle  which 
variety,  whether  a  smooth  or  downy,  a  yellow  or  a  purple- 
fleshed  fruit,  should  succeed. 

In  looking  at  many  small  points  of  difference  between 
species,  which,  as  far  as  our  ignorance  permits  us  to  judge, 
seem  quite  unimportant,  we  must  not  forget  that  climate, 
food,  etc.,  have  no  doubt  produced  some  direct  effect.  It 
is  also  necessary  to  bear  in  mind  that,  owing  to  the  law  of 
correlation,  when  one  part  varies  and  the  variations  are 
accumulated  through  natural  selection,  other  modifica¬ 
tions,  often  of  the  most  unexpected  nature,  will  ensue. 

As  we  see  that  those  variations  which,  under  domesti¬ 
cation,  appear  at  any  particular  period  of  life,  tend  to 
reappear  in  the  offspring  at  the  same  period;  for  instance, 
in  the  shape,  size  and  flavor  of  the  seeds  of  the  many 
varieties  of  our  culinary  and  agricultural  plants;  in  the 
caterpillar  and  cocoon  stages  of  the  varieties  of  the  silk¬ 
worm;  in  the  eggs  of  poultry,  and  in  the  color  of  the  down 
of  their  chickens;  in  the  horns  of  our  sheep  and  cattle 
when  nearly  adult;  so  in  a  state  of  nature  natural  selection 
will  be  enabled  to  act  on  and  modify  organic  beings  at  any 
age,  by  the  accumulation  of  variations  profitable  at  that 
age,  and  by  their  inheritance  at  a  corresponding  age.  If  it 
profit  a  plant  to  have  its  seeds  more  and  more  widely  dis¬ 
seminated  by  the  wind,  I  can  see  no  greater  difficulty  in 
this  being  effected  through  natural  selection,  than  in  the 
cotton-planter  increasing  and  improving  by  selection  the 
down  in  the  pods  on  his  cotton-trees.  Natural  selection 
may  modify  and  adapt  the  larva  of  an  insect  to  a  score  of 
contingencies,  wholly  different  from  those  which  concern 
the  mature  insect;  and  these  modifications  may  effect, 
through  correlation,  the  structure  of  the  adult.  So,  con¬ 
versely,  modifications  in  the  adult  may  affect  the  structure 
of  the  larva;  but  in  all  cases  natural  selection  will  insure 
that  they  shall  not  be  injurious:  for  if  they  were  so.  the 
species  would  become  extinct. 

Natural  selection  will  modify  the  structure  of  the  young 
in  relation  to  the  parent  and  of  the  parent  in  relation  to 
the  young.  In  social  animals  it  will  adapt  the  structure  of 
each  individual  for  the  benefit  of  the  whole  community; 
if  the  community  profits  by  the  selected  change.  "What 


NATURAL  SELECTION \ 


80 

natural  selection  cannot  do,  is  to  modify  the  structure  of 
one  species,  without  giving  it  any  advantage,  for  the  good 
of  another  species;  and  though  statements  to  this  effect 
may  be  found  in  works  of  natural .  history,  I  cannot  find 
one  case  which  will  bear  investigation.  A  structure  used 
only  once  in  an  animal's  life,  if  of  high  importance  to 
it,  might  be  modified  to  any  extent  by  natural  selection; 
for  instance,  the  great  jaws  possessed  by  certain  insects, 
used  exclusively  for  opening  the  cocoon — or  the  hard  tip  to 
the  beak  of  unhatched  birds,  used  for  breaking  the  eggs. 
It  has  been  asserted,  that  of  the  best  short-beaked  tumbler- 
pigeons  a  greater  number  perish  in  the  egg  than  are  able  to 
get  out  of  it;  so  that  fanciers  assist  in  the  act  of  hatching. 
Now,  if  nature  had  to  make  the  beak  of  a  full-grown  pigeon 
very  short  for  the  bird's  own  advantage,  the  process  of 
modification  would  be  very  slow,  and  there  would  be  simul¬ 
taneously  the  most  rigorous  selection  of  all  the  young  birds 
within  the  egg,  which  had  the  most  powerful  and  hardest 
beaks,  for  all  with  weak  beaks  would  inevitably  perish;  or, 
more  delicate  and  more  easily  broken  shells  might  be 
selected,  the  thickness  of  the  shell  being  known  to  vary 
like  every  other  structure. 

It  may  be  well  here  to  remark  that  with  all  beings  there 
must  be  much  fortuitous  destruction,  which  can  have 
little  or  no  influence  on  the  course  of  natural  selection. 
For  instance,  a  vast  number  of  eggs  or  seeds  are 
annually  devoured,  and  these  could  be  modified  through 
natural  selection  only  if  they  varied  in  some  manner 
which  protected  them  from  their  enemies.  Yet  many  of 
these  eggs  or  seeds  would  perhaps,  if  not  destroyed,  have 
yielded  individuals  better  adapted  to  their  conditions  of 
life  than  any  of  those  which  happened  to  survive.  So 
again  a  vast  number  of  mature  animals  and  plants,  whether 
or  not  they  be  the  best  adapted  to  their  conditions,  must 
be  annually  destroyed  by  accidental  causes,  which  would 
not  be  in  the  least  degree  mitigated  by  certain  changes  of 
structure  or  constitution  which  would  in  other  ways  be 
beneficial  to  the  species.  But  let  the  destruction  of  the  adults 
be  ever  so  heavy,  if  the  number  which  can  exist  in  any  dis¬ 
trict  be  not  wholly  kept  down  by  such  causes — or  again  let 
the  destruction  of  eggs  or  seeds  be  so  great  that  onl}r  a 
hundredth  or  a  thousandth  part  are  developed — yet  of 


SEXUAL  SELECTION, . 


81 


those  which  do  survive,  the  best  adapted  individuals,  sup- 
I  posing  that  there  is  any  variability  in  a  favorable  direction, 

I  will  tend  to  propagate  their  kind  in  larger  numbers  than 
I  the  less  well  adapted.  If  the  numbers  be  wholly  kept 
udown  by  the  causes  just  indicated,  as  will  often  have  been 
the  case,  natural  selection  will  be  powerless  in  certain  ben¬ 
eficial  directions;  but  this  is  no  valid  objection  to  its  effi¬ 
ciency  at  other  times  and  in  other  ways;  for  we  are  far 
from  having  any  reason  to  suppose  that  many  species  ever 
undergo  modification  and  improvement  at  the  same  time 
in  the  same  area. 


SEXUAL  SELECTION-. 

Inasmuch  as  peculiarities  often  appear  under  domestica¬ 
tion  in  one  sex  and  become  hereditarily  attached  to  that 
sex,  so  no  doubt  it  will  be  under  nature.  Thus  it  is  ren¬ 
dered  possible  for  the  two  sexes  to  be  modified  through 
natural  selection  in  relation  to  different  habits  of  life,  as  is 
sometimes  the  case;  or  for  one  sex  to  be  modified  in  rela¬ 
tion  to  the  other  sex,  as  commonly  occurs.  This  leads  me 
to  say  a  few  words  on  what  I  have  called  sexual  selection. 
This  form  of  selection  depends,  not  on  a  struggle  for  exist- 
tence  in  relation  to  other  organic  beings  or  to  external 
conditions,  but  on  a  struggle  between  the  individuals  of 
one  sex,  generally  the  males,  for  the  possession  of  the  other 
sex.  The  result  is  not  death  to  the  unsuccessful  competi¬ 
tor,  but  few  or  no  offspring.  Sexual  selection  is,  there¬ 
fore,  less  rigorous  than  natural  selection.  Generally,  the 
most  vigorous  males,  those  which  are  best  fitted  for  their 
places  in  nature,  will  leave  most  progeny.  But  in  many 
cases  victory  depends  not  so  much  on  general  vigor,  a  son 
having  special  weapons,  confined  to  the  male  sex.  A  horn¬ 
less  stag  or  spurless  cock  would  have  a  poor  chance  of 
leaving  numerous  offspring.  Sexual  selection,  by  always 
allowing  the  victor  to  breed,  might  surely  give  indomitable 
courage,  length  of  spur  and  strength  to  the  wing  to  strike 
in  the  spurred  leg,  in  nearly  the  same  manner  as  does  the 
brutal  cockfighter  by  the  careful  selection  of  his  best  cocks. 
How  low  in  the  scale  of  nature  the  law  of  battle  descends 
I  know  not;  male  alligators  have  been  described  as  fight¬ 
ing,  bellowing  and  whirling  round,  like  Indians  in  a  war- 
dance,  for  the  possession  of  the  females;  male  salmons  have 


82 


SEXUAL  SELECTION. 


been  observed  fighting  all  day  long;  male  stag-beetles 
sometimes  bear  wounds  from  the  huge  mandibles  of  other 
males;  the  males  of  certain  hymenopterous  insects  have 
been  frequently  seen  by  that  inimitable  observer  M* 
Fabre,  fighting  for  a  particular  female  who  sits  by,  an  ap¬ 
parently  unconcerned  beholder  of  the  struggle,  and  then 
retires  with  the  conqueror.  The  war  is,  perhaps,  severest 
between  the  males  of  polygamous  animals,  and  these  seem 
oftenest  provided  with  special  weapons.  The  males  of 
carnivorous  animals  are  already  well  armed;  though  to 
them  and  to  others,  special  means  of  defence  may  be 
given  through  means  of  sexual  selection,  as  the  mane  of 
the  lion,  and  the  hooked  jaw  to  the  male  salmon;  for  the 
shield  may  be  as  important  for  victory  as  the  sword  or 
spear. 

Among  birds,  the  contest  is  often  of  a  more  peaceful 
character.  All  those  who  have  attended  to  the  subject, 
believe  that  there  is  the  severest  rivalry  between  the  males 
of  many  species  to  attact,  by  singing,  the  females.  The 
rock-thrush  of  Guiana,  birds  of  paradise,  and  some  others, 
congregate,  and  successive  males  display  with  the  most 
elaborate  care,  and  show  off  in  the  best  manner,  their 
gorgeous  plumage;  they  likewise  perform  strange  antics 
before  the  females,  which,  standing  by  as  spectators,  at 
last  choose  the  most  attractive  partner.  Those  who  have 
closely  attended  to  birds  in  confinement  well  know  that 
they  often  take  individual  preferences  and  dislikes:  thus 
Sir  R.  Heron  has  described  how  a  pied  peacock  was  emi¬ 
nently  attractive  to  all  his  hen  birds.  I  cannot  here  enter 
on  the  necessary  details;  but  if  man  can  in  a  short  time 
give  beauty  and  an  elegant  carriage  to  his  bantams,  accord¬ 
ing  to  his  standard  of  beauty,  I  can  see  no  good  reason  to 
doubt  that  female  birds,  by  selecting,  during  thousands  of 
generations,  the  most  melodious  or  beautiful  males,  accoid- 
to  their  standard  of  beauty,  might  produce  a  marked 
effect.  Some  well-known  laws,  with  respect  to  the  pumage 
of  male  and  female  birds,  in  comparison  with  the  plumage 
of  the  young,  can  partly  be  explained  through  the  action 
of  sexual  selection  on  variations  occurring  at  different 
ages,  and  transmitted  to  the  males  alone  or  to  both  sexes 
at  corresponding  ages;  but  I  have  not  space  here  to  enter 
on  this  subject.  '' 


SEXUAL  SELECTION.  go 

of^nvVnim^fjn.vp1^6’  tbat  when  tbe  ma,es  and  females 

01  anj_animal  have  the  same  general  habits  of  life  W 

jhffer  .n  structure,  color,  or  Srnament,  such  differences 

have  been  mainly  caused  by  sexual  selection-  that  is  bv 

individual  males  having  had,  in  successh^generatLs7 

some  slight  advantage  over  other  males,  in  their  weapons' 

means  of  defense,  or  charms,  which  they  have  transmitted 

o  thw  mate  offspring  alone.  Yet,  I  wonld  noWteh  to 

attnbute  all  sexual  differences  to  this  agency:  for  we  see 

attachedbTthc  m„TalS  peo"!iarities  arising  and  becoming 
attacned  to  the  male  sex,  which  apparently  have  not  been 

thf  brTasf  ofTh^  by  m  i n*  The  tuft  of  hair  on 

and  itifd n?Lfht  n1ltUr-xey-C00k  cannot  be  of  any  use, 
and  it  is  doubtful  whether  it  can  be  ornamental  in  the  eves 

of  the  female  bird;  indeed,  had  the  tuft  appeared  under 

domestication  it  would  have  been  called  a  monstrosity. 

illustrations  op  the  action  of  natural  selection 

OR,  THE  SURVIVAL  OP  THE  FITTEST 

tionbcts 6 1  m nst^V?  cIear.h?w>  as  1  Relieve,  natural  selec- 
non  acts,  1  must  beg  permission  to  give  one  or  two  imam 

nary  illustrations.  Let  us  take  the  case  of  a  wolf  which 

preys  on  various  animals,  securing  some  bv  craft  some  bv 

strength,  and  some  by  fleetness;  and  let  “us  suppose  that 

the  fleetest  prey,  a  deer  for  instance,  had  from  any  change 

m  the  country  increased  in  numbers  or 

ye'ar  whldetCheeawo1fin  n\mb®r%during  ^at  season  of  the 
year  wlien  the  wolf  was  hardest  pressed  for  food  Under 

he ^  bestCnchanceCeofhe  8Wi-f,?St  and  slimmest  "'°'lves 
tne  pest  ciiance  of  surviving,  and  so  be  preserved  or 

selected,  provided  always  that  they  retained  streno-j-L  fn 

master  their  prey  at  this  or  some  ofhei -  period  of  thl  v  a 

when  they  were  compelled  to  prey  on  other  animals  I  can 

see  no  more  reason  to  doubt  that  this  would  be  the  resnft 

than  that  man  should  be  able  to  improve  the  fleetness  of  his 

grevhounds  by  careful  and  methodical  selection  or  by  that 

kind  of  unconscious  selection  which  follows  from  each  man 

ifvirw  tv  kenP  4 16  bTSt  d0gS  without  any  thought  of  mod- 
»*"*  tbe  breed-  1  may  add  that,  according  to  Mr 

p  f  ?e-’utUe  are  two  varieties  of  the  wolf  inhabiting  the 
Gatskili  Mountains,  in  the  United  States,  one  with  a  fight 


84  illustrations  of  tub  action 

srevViound-like  form,  which  pursues  deer,  and  the  other 
more  bulky,  with  shorter  legs,  which  more  frequently 

attacks  the  shepherd  s  flocks.  ......  t 

It  should  be  observed  that  in  the  above  illustration,  I 
speak  of  the  slimmest  individual  wolves,  and  not  of  any 
single  strongly  marked  variation  having  been  preserved. 
In  former  editions  of  this  work  I  sometimes  spoke  as  if 
this  latter  alternative  had  frequently  occurred.  I  saw  lie 
great  importance  of  individual  differences,  and  this  led 
me  fully  to  discuss  the  results  of  unconscious  selection  by 
man,  which  depends  on  the  preservation  of  all  the  more  or 
less  valuable  individuals,  and  on  the  destruction  of  the 
worst.  I  saw,  also,  that  the  preservation  m  a  state  ot 
nature  of  any  occasional  deviation  of  structure,  such  as  a 
monstrosity,  would  be  a  rare  event;  and  that,  if  at  hist 
preserved,  it  would  generally  be  lost  by  suosequent  inter¬ 
crossing  with  ordinary  individuals.  Nevertheless,  unti 
reading  an  able  and  valuable  article  in  the  “  North  British 
Review”  (1867),  I  did  not  appreciate  how  rarely  single 
variations,  whether  slight  or  strongly  marked,  could  be 
perpetuated.  The  author  takes  the  case  of  a  pair  ot  am- 
£  producing  during  their  lifetime  two  hundred 
offspring,  of  which,  from  various  causes  of  destruction, 
only  two  on  an  average  survive  to  pro-create  their  kmc . 
This  is  rather  an  extreme  estimate  for  most  of  the  higher 
animals  but  by  no  means  so  for  many  of  _  the  lower  organ¬ 
isms  He  then  shows  that  if  a  single  individual  were  born, 
which  varied  in  some  manner,  giving  it  twice  as  good  a 
chance  of  life  as  that  of  the  other  individuals,  yet  the 
chances  would  be  strongly  against  its  survival.  Supposing 
it  to  survive  and  to  breed,  _  and  that  half  its  yoi  g 
inherited  the  favorable  variation;  still,  as  the  Reviewer 
o-oes  on  to  show,  the  young  would  have  only  a  slightly 
better  chance  of  surviving  and  breeding;  and  this  chance 
would  go  on  decreasing  in  the  succeeding  generations. 
The  -justice  of  these  remarks  cannot,  I  think,  be 
disuuted  If,  for  instance,  a  bird  of  some  kind  could 
procure  its  food  more  easily  by  having  its  beak  curved, 
and  if  one  were  born  with  its  beak  strongly  curved, 
and  which  consequently  flourished,  nevertheless  them 
would  be  a  very  poor  chance  of  this  one  individual  perpet¬ 
uating  its  kind  to  the  exclusion  of  the  common  form;  but 


OF  NATURAL  SELECTION  85 

there  can  hardly  be  a  doubt,  judging  by  what  we  see  taking 
place  under  domestication,  that  this  result  would  follow 
fiom  the  preservation  during  many  generations  of  a  laro-e 
numbei  of  individuals  with  more  or  less  strongly  curved 
beaks,  and  from  the  destruction  of  a  still  larger  number 
with  the  straightest  beaks. 

It  should  not,  however,  be  overlooked  that  certain 
rather  strongly  marked  variations,  which  no  one  would 
lank  as  mere  individual  differences,  frequently  recur 
owmg  to  a  similar  organization  being  similarly  acted  on — - 
ol  which  fact  numerous  instances  could  be  given  with  our 
domestic  productions.  In  such  cases,  if  the  varying  indi¬ 
vidual  did  not  actually  transmit  to  its  offspring  its  "newly- ' 
acquired  character,  it  would  undoubtedly  transmit  to  them 
as  ong  as  the  existing  conditions  remained  the  same,  a 
still  stronger  tendency  to  vary  in  the  same  manner.  There 
can  also  be  little  doubt  that  the  tendency  to  vary  in  the 
same  manner  has  often  been  so  strong  that  all  the  individ¬ 
uals  of  the  same  species  have  been  similarly  modified  with- 
fche  ,aid1of  any  foi'm  of  selection.  Or  only  a  third, 

1  03*  dentil  part  of  the  individuals  may  have  been  thus 
affected,  of  which  fact  several  instances  could  be  given. 
Thus  Grraba  estimates  that  about  one-fifth  of  the  guille¬ 
mots  in  the  Faroe  Islands  consist  of  a  variety  so  well 
marked,  that  it  was  formerly  ranked  as  a  distinct  species 
under  the  name  of  Uria  lacrymans.  In  cases  of  this  kind, 
it  the  vaiiation  were  of  a  beneficial  nature,  the  original 
form  would  soon  be  supplanted  by  the  modified  form 
through  the  survival  of  the  fittest.  9 

.  ^ie  fects  of  intercrossing  in  eliminating  variations  of 
all  kinds,  I  shall  have  to  recur;  but  it  maybe  here  remarked 
that  most. animals  and  plants  keep  to  their  proper  homes, 
and  do  not  needlessly  wander  about;  we  see  this  even  with 
migratory  birds,  which  almost  always  return  to  the  same 
spot.  Consequently  each  newly-formed  variety  would  gen¬ 
erally  be  at  first  local,  as  seems  to  be  the  common  rule  with 
varieties  in  a  state  of  nature;  so  that  similarly  modified.indi- 
viduals  would  soon  exist  in  a  small  body  together  and 
would  often  breed  together.  If  the  new  variety  were  suc¬ 
cessful  in  its  battle  for  life,  it  would  slowly  spread  from  a 
central  district,  competing  with  and  conquering  the  un¬ 
changed  individuals  ou  the  margins  of  an  ever-increasing 
circle* 


86  ILL  USTRA  TIONS  OF  THE  ACTION 

It  may  be  worth  while  to  give  another  and  more  complex 
illustration  of  the  action  of  natural  selection.  Certain 
plants  excrete  sweet  juice,  apparently  for  the  sake  of  elim¬ 
inating  something  injurious  from  the  sap:  this  is  effected, 
for  instance,  by  glands  at  the  base  of  the  stipules  m  some 
Leguminosse,  and  at  the  backs  of  the  leaves  of  the  common 
laurel.  This  juice,  though  small  m  quantity,  is  greedily 
sought  by  insects;  but  their  visits  do  not  m. any  way  ben¬ 
efit  the  plant.  Now,  let  us  suppose  that  the  juice  or  nectar 
was  excreted  from  the  inside  of  the  flowers  of  a  ceitarn 
number  of  plants  of  any  species.  Insects  m  seeking  the 
nectar  would  get  dusted  with  pollen,  and  would  often 
transport  it  from  one  flower  to  another.  The  flowers  of 
two  distinct  individuals  of  the  same  species  would  thus  get 
crossed;  and  the  act  of  crossing,  as  can  be  fully  proved, 
gives  rise  to  vigorous  seedlings,  which  consequently  would 
have  the  best  chance  of  flourishing  and  surviving.  ie 
plants  which  produced  flowers  with  the  largest  glands  or 
nectaries,  excreting  most  nectar,  would  oftenest  be  visited 
by  insects,  and  would  oftenest  be  crossed;  and  so  in  the 
long-run  would  gain  the  upper  hand  and  form  a  local 
variety.  The  flowers,  also,  which  had  their  stamens  and 
pistils  placed,  in  relation  to  the  size  and  habits  of  the  par¬ 
ticular  insect  which  visited  them,  so  as  to  favor  in  any 
decree  the  transportal  of  the  pollen,  would  likewise  be 
favored.  We  might  have  taken  the  case  of  insects  visiting 
flowers  for  the  sake  of  collecting  pollen  instead  of  nectar; 
and  as  pollen  is  formed  for  the  sole  purpose  of  fertilization, 
its  destruction  appears  to  be  a  simple  loss  to  the  plant;  yet 
if  a  little  pollen  were  carried,  at  first  occasionally  and  then 
habitually,  by  the  pollen-devouring  insects  from  flower  to 
flower,  and  a  cross  thus  effected,  although  nine-tenths  of 
the  pollen  were  destroyed  it  might  still  be  a  great  gain  to 
the  plant  to  be  thus  robbed;  and  the  individuals  which 
produced  more  and  more  pollen,  and  had  larger  anthers, 

would  be  selected.  , 

When  our  plant,  by  the  above  process  long  continued, 

had  been  rendered  highly  attractive  to  insects,  they  would, 
unintentionally  on  their  part,  regularly  carry  pollen  from 
flower  to  flower;  and  that  they  do  this  effectually  I  cou  c 
easily  show  by  many  striking  facts.  I  will  give  only  one, 
as  likewise  illustrating  one  step  in  the  separation  of  the 


OF  NATURAL  SELECTION.  37 

sexes  of  plants.  Some  holly-trees  bear  only  male  flowers 
which  have  four  stamens  producing  a  rather  small  quan¬ 
tity  of  pollen,  and  a  rudimentary  pistil;  other  holly-trees 
bear  only  female  flowers;  these  have  a  full-sized  pistil,  and 
four  stamens  with  shrivelled  anthers,  in  which  not  a  grain 
of  polen  can  be  detected.  Having  found  a  female  tree 
exactly  sixty  yards  from  a  male  tree,  I  put  the  stigmas  of 
twenty  flowers,  taken  from  different  branches,  under  the 
nncioscope,  and  on  all,  without  exception,  there  were  a  few 
pollen-grains,  and  on  some  a  profusion.  As  the  wind  had 
set  for  several  days  from  the  female  to  the  male  tree,  the 
pollen  could  not  thus  have  been  carried.  The  weather 
had  been  cold  and  boisterous  and  therefore  not  favorable 
to  bees,  nevertheless  every  female  flower  which  I  examined 
had  been  effectually  fertilized  bv  the  bees,  which  had  flown 
irorn  tree  to  tree  in  search  of  nectar.  But  to  return  to 
our  imaginary  case;  as  soon  as  the  plant  had  been  ren¬ 
dered  so  highly  attractive  to  insects  that  pollen  was  regu¬ 
larly  carried  from  flower  to  flower,  another  process  might 
commence.  No  naturalist  doubts  the  advantage  of  what 
has  been  called  the  “  physiological  division  of  labor;”  hence 
we  may  believe  that  it  would  be  advantageous  to  a  plant  to 
produce  stamens  alone  in  one  flower  or  on  one  whole  plant 
and  pistils  alone  in  another  flower  or  on  another  plant! 

*  V?nts  unc^e.r  culture  and  placed  under  new  conditions 
01  life,  sometimes  the  male  organs  and  sometimes  the 
female  organs  become  more  or  less  impotent;  now  if  we 
suppose  this  to  occur  in  ever  so  slight  a  degree  under 
nature,  then,  as  pollen  is  already  carried  regularly  from 
flowei  to  flower,  and  as  a  more  complete  separation  of  the 
sexes  of  our  plant  would  be  advantageous  on  the  principle 
of  the  division  of  labor,  individuals  with  this  tendency 
more  and  more  increased,  would  be  continually  favored  or 
selected,  until  at  last  a  complete  separation  of  the  sexes 
might  be  effected.  It  would  take  up  too  much  space  to 
show  the  various  steps,  though  dimorphism  and  other 
means,  by  which  the  separation  of  the  sexes  in  plants  of 
various  kinds  is  apparently  now  in  progress;  but  I  may 
add  that  some  of  the  species  of  holly  in  North  America 
are  according  to  Asa  Gray,  in  an  exactly  intermediate 
condition,  or,  as  he  expresses  it,  are  more  or  less  dioeciously 
polygamous.  J 


Sg  ILLUSTRATIONS  OF  THE  ACTION 

Let  us  now  turn  to  the  nectar-feeding  insects;  we  may 
suppose  the  plant,  of  which  we  have  been  slowly  increasing 
the  nectar  by  continued  selection,  to  be  a  common  plant; 
and  that  certain  insects  depended  in  mam  part  on  its 
nectar  foi  food.  I  could  give  many  facts  showing  how 
anxious  bees  are  to  save  time:  for  instance,  their  habit  o 
cuttino-  holes  and  sucking  the  nectar  at  the  bases  of  ceitain 
dowers,  which  with  a  very  little  more  trouble  they  can  enter 
by  the  mouth.  Bearing  such  facts  in  mind,  it  maybe  believed 
that  under  certain  circumstances  individual  differences  m 
the  curvature  or  length  of  the  probocis,  etc.,  too  slight  to  e 
appreciated  by  us,  might  profit  a  bee  or  other  insect  so 
that  certain  individuals  would  be  able  to  obtain  then  food 
more  quickly  than  others;  and  thus  the  communities  to 
which  they  belonged  would  dourish  and  throw  off  many 
swarms  inheriting  the  same  peculiarities.  -The  tubes  of 
the  corolla  of  the  common  red  or  incarnate  clovers  (irito- 
liurn  pratense  and  incarnatum)  do  not  on  a  hasty  glance 
appear  to  differ  in  length;  yet  the  hive-bee  can  easily  suck 
the  nectar  out  of  the  incarnate  clover,  but  not  out  of  the 
common  red  clover,  which  is  visited  by  humble-bees  alone, 
so  that  whole  delds  of  the  red  clover  offer  m  vam  an  abun¬ 
dant  supply  of  precious  nectar  to  the.  hive-bee.  That  this 
nectar  is  much  liked  by  the  hive-bee  is  certain;  for  I  have 
repeatedly  seen,  but  only  in  the  autumn,  many  hive-bees 
sucking  the  dowers  through  holes  bitten  m  the  base  of  the 
tube  by  humble-bees.  The  difference  in  the  length  of  the 
corolla  in  the  two  kinds  of  clover,  which  determines  the 
visits  of  the  hive-bee,  must  be  very  tndmg;  for  I  have  been 
assured  that  when  red  clover  has  been  mown  the  dowers 
of  the  second  crop  are  somewhat  smaller,  and  that  these 
are  visited  by  many  hive-bees.  I  do  not  know  whether 
this  statement  is  accurate;  nor  whether  another  published 
statement  can  be  trusted,  namely,  that  the  Ligurian  bee, 
which  is  generally  considered  a  mere  variety  of  the  com¬ 
mon  hive-bee,  and  which  freely  crosses  with  it,  is  able  to 
reach  and  suck  the  nectar  of  the  red  clover.  Thus,  in  a 
country  where  this  kind  of  clover  abounded,  it  might  oe 
a  great  advantage  to  the  hive-bee  to  have  a  slightly  longer 
or  differently  constructed  proboscis.  On  the  other  hand, 
as  the  fertility  of  this  clover  absolutely  depends  on  bees  vis¬ 
iting  the  dowers,  if  humble-bees  were  to  become  rare  m  any 


OF  NATURAL  SELECTION. 


So 


country,  it  might  be  a  great  advantage  to  the  plant  to  have 
a  shorter  or  more  deeply  divided  corolla,  so  that  the  hive- 
bees  should  be  enabled  to  suck  its  flowers.  Thus  I  can  un¬ 
derstand  how  a  dower  and  a  bee  might  slowly  become, 
either  simultaneously  or  one  after  the  other,  modified  and 
adapted  to  each  other  in  the  most  perfect  manner,  by 
the  continued  preservation  of  all  the  individuals  which 
presented  slight  deviations  of  structure  mutually  favorable 
to  each  other. 

I  am  well  aware  that  this  doctrine  of  natural  selection, 
exemplified  in  the  above  imaginary  instances,  is  open  to 
the  same  objections  which  were  first  urged  against  Sir 
Charles  Lyelfis  noble  views  on  “  the  modern  changes  of 
the  earth,  as  Illustrative  of  geology;”  but  we  now  seldom 
hear  the  agencies  which  we  see  still  at  work,  spoken  of  as 
trifling  or  insignificant,  when  used  in  explaining  the  excava¬ 
tion  of  the  deepest  valleys  or  the  formation  of  long  lines  of 
inland  cliffs.  Natural  selection  acts  only  by  the  preserva¬ 
tion  and  accumulation  of  small  inherited  modifications, 
each  profitable  to  the  preserved  being;  and  as  modern  geol¬ 
ogy  has  almost  banished  such  views  as  the  excavation  of  a 
great  valley  by  a  single  diluvial  wave,  so  will  natural  selec¬ 
tion  banish  the  belief  of  the  continued  creation  of  new  or¬ 
ganic  beings,  or  of  any  great  and  sudden  modification  in 
their  structure. 

ON  THE  INTERCROSSING  OF  INDIVIDUALS. 

I  must  here  introduce  a  short  digression.  In  the  case  of 
animals  and  plants  with  separated  sexes,  it  is  of  course  ob¬ 
vious  that  two  individuals  must  always  (with  the  ex¬ 
ception  of  the  curious  and  not  well  understood  cases  of 
parthenogenesis)  unite  for  each  birth;  but  in  the  case  of 
hermaphrodites  this  is  far  from  obvious.  Nevertheless 
there  is  reason  to  believe  that  with  all  hermaphrodites  two 
individuals,  either  occasionally  or  habitually,  concur  for 
the  reproduction  of  their  kind.  This  view  was  long  ago 
doubtfully  suggested  by  Sprengel  Knight  and  Kolreuter. 
We  shall  presently  see  its  importance;  but  I  must  here 
Sreat  the  subject  with  extreme  brevity,  though  I  have  the 
materials  prepared  for  an  ample  discussion.  All  vertebrate 
animals,  all  insects  and  some  other  large  groups  of  animals. 


90 


ON  THE  INTERCROSSING 


pair  for  each  birth.  Modern  research  has  much  diminished 
the  number  of  supposed  hermaphrodites  and  of  real  herma¬ 
phrodites  a  large  number  pair;  that  is,  two  individuals  regu¬ 
larly  unite  for  reproduction,  which  is  all  that  concerns  us. 
But  still  there  are  many  hermaphrodite  animals  which  cer¬ 
tainly  do  not  habitually  pair,  and  a  vast  majority  of  plants 
are  hermaphrodites.  What  reason,  it  may  be.  asked,  is 
there  for  supposing  in  these  cases  that  two  individuals  ever 
concur  in  reproduction?  As  it  is  impossible  here  to  enter 
on  details,  I  must  trust  to  some  general  considerations 
alone. 

In  the  first  place,  I  have  collected  so  large  a  body  of 
facts,  and  made  so  many  experiments,  showing,  in  accord¬ 
ance  with  the  almost  universal  belief  of  breeders,  that  with 
animals  and  plants  a  cross  between  different  varieties,  or 
between  individuals  of  the  same  variety  but  of  another 
strain,  gives  vigor  and  fertility  to  the  offspring;  and  on 
the  other  hand,  that  close  interbreeding  diminishes  vigor 
and  fertility;  that  these  facts  alone  incline  me  to  believe 
that  it  is  a  general  law  of  nature  that  no  organic  being 
fertilizes  itself  for  a  perpetuity  of  generations;  but  that  a 
cross  with  another  individual  is  occasionally — perhaps  at 
long  intervals  of  time — indispensable. 

On  the  belief  that  this  is  a  law  of  nature,  we  can,  I 
think,  understand  several  large  classes  of  facts,  such  as 
the  following,  which  on  any  other  view  are  inexplicable. 
Every  hybridizer  knows  how  unfavorable  exposure  to  wet 
is  to  the  fertilization  of  a  flower,  yet  what  a  multitude  of 
flowers  have  their  anthers  and  stigmas  fully  exposed  to  the 
weather  1  If  an  occasional  cross  be  indispensable,  notwith¬ 
standing  that  the  plant’s  own  anthers  and  pistil  stand  so 
near  each  other  as  almost  to  insure  self-fertilization,  the 
fullest  freedom  for  the  entrance  of  pollen  from  another  in¬ 
dividual  will  explain  the  above  state  of  exposure  of  the 
organs.  Many  flowers,  on  the  other  hand,  have  their 
organs  of  fructification  closely  inclosed,  as  in  the  great 
papilionaceous  or  pea-family;  but  these  almost  invariably 
present  beautiful  and  curious  adaptations  in  relation  to  the 
visits  of  insects.  So  necessary  are  the  visits  of  bees  to 
many  papilionaceous  flowers,  that  their  fertility  is  greatly 
diminished  if  these  visits  be  prevented.  Eow,  it  is  scarcely 
possible  for  insects  to  fly  from  flower  to  flower,  and  not  to 


OF  INDIVIDUALS. 


fil 

carry  pollen  from  one  to  tlie  other,  to  the  great  good  of  the 
plant.  Insects  act  like  a  camel-hair  pencil,  and  it  is  suffi¬ 
cient,  to  insure  fertilization,  just  to  touch  with  the  same 
brush  the  anthers  of  one  flower  and  then  the  stigma  of 
another;  but  it  must  not  be  supposed  that  bees  would  thus 
produce  a  multitude  of  hybrids  between  distinct  species; 
for  if  a  plant’s  own  pollen  and  that  from  another  species 
are  placed  on  the  same  stigma,  the  former  is  so  prepotent 
that  it  invariably  and  completely  destroys,  as  has"  been 
shown  by  Gartner,  the  influence  of  the  foreign  pollen. 

"W  hen  the  stamens  of  a  flower  suddenly  spring  toward 
the  pistil,  or  slowly  move  one  after  the  other  toward 
it,  the  contrivance  seems  adapted  solely  to  ensure  self- 
fertilization;  and  no  doubt  it  is  useful  for  this  end:  but 
the  agency  of  insects  is  often  required  to  cause  the  stamens 
to  spring  forward,  as  Kolreuter  has  shown  to  be  the  case 
with  the  barberry;  and  in  this  very  genus,  which  seems  to 
have  a  special  contrivance  for  self-fertilization,  it  is  well 
known  that,  if  closely-allied  forms  or  varieties  are  planted 
near  each  other,  it  is  hardly  possible  to  raise  pure  seedlings, 
so  largely  do  they  naturally  cross.  In  numerous  other 
cases,  far  from  self-fertilization  being  favored,  there  are 
special  contrivances  which  effectually  prevent  the  stigma 
receiving  pollen  from  its  own  flower,  as  I  could  show  from 
the  works  of  Sprengel  and  others,  as  well  as  from  my  own 
observations:  for  instance,  in  Lobelia  fulgens,  there  is 
a  really  beautiful  and  elaborate  contrivance  by  which  all 
the  infinitely  numerous  pollen-granules  are  swept  out  of 
the  conjoined  anthers  of  each  flower,  before  the  stigma  of 
that  individual  flower  is  ready  to  receive  them;  and  as  this 
flower  is  never  visited,  at  least  in  my  garden,  by  insects,  it 
never  sets  a  seed,  though  by  placing  pollen  from  one  flower 
on  the  stigma  of  another,  I  raise  plenty  of  seedlings. 
Another  species  of  Lobelia,  which  is  visited  by  bees,  seeds 
freely  in  my  garden.  In  very  many  other  cases,  though 
there  is  no  special  mechanical  contrivance  to  prevent  the 
stigma  receiving  pollen  from  the  same  flower,  yet,  as 
Sprengel,  and  more  recently  Hildebrand  and  others  have 
shown,  and  as  I  can  confirm,  either  the  anthers  burst 
before  the  stigma  is  ready  for  fertilization,  or  the  stigma  is 
ready  before  the  pollen  of  that  flower  is  ready,  so  that  these 
so-named  dichogamous  plants  have  in  fact  separated  sexes. 


92 


ON  THE  INTERCROSSING 


and  must  habitually  be  crossed.  So  it  is  with  the  recipro¬ 
cally  dimorphic  and  trimorphic  plants  previously  alluded 
to.  How  strange  are  these  facts!  How  strange  that  the 
pollen  and  stigmatic  surface  of  the  same  flower,  though 
placed  so  close  together,  as  if  for  the  very  purpose  of  self- 
fertilization,  should  be  in  so  many  cases  mutually  useless 
to  each  other?  How  simply  are  these  facts  explained  on 
i  the  view  of  an  occasional  cross  with  a  distinct  individual 
i  being  advantageous  or  indispensable!  .  , 

If  several  varieties  of  the  cabbage,  radish,  onion  and  of 
some  other  plants,  be  allowed  to  seed  near  each  other,  a 
large  majority  of  the  seedling  thus  raised  turn  out,  as  1 
founds  mongrels:  for  instance,  I  raised  233  seedling  cab¬ 
bages  from  some  plants  of  different  varieties  growing  near 
each  other,  and  of  these  only  78  were  true  to  their  kind 
and  some  even  of  these  were  not  perfectly  true.  Yet  the 
pistil  of  each  cabbage-flower  is  surrounded  not  only  by  its 
own  six  stamens  but  by  those  of  the  many  other  flowers  on 
the  same  plant;  and  the  pollen  of  each  flower  readily  gets 
on  its  stigma  without  insect  agency;  for  I  have  found  that 
plants  carefully  protected  from  insects  produce  the  lull 
number  of  pods.  How,  then,  comes  it  that  such  a  vast 
number  of  the  seedlings  are  mongrelized?.  It  must  arise 
from  the  pollen  of  a  distinct  variety  having  a  prepotent 
effect  over  the  flower's  own  pollen;  and  that  this  is  part  ot 
the  general  law  of  good  being  derived  from  the  intercross¬ 
ing  of  distinct  individuals  of  the  same  species.  When  dis¬ 
tinct  species  are  crossed  the  case  is  reversed,  for  a  plant  s 
own  pollen  is  almost  always  prepotent  over  foreign  pollen; 
but  to  this  subject  we  shall  return  in  a  future  chapter. 

In  the  case  of  a  large  tree  covered  with  innumerable 
flowers,  it  may  be  objected  that  pollen  could  seldom  be 
carried  from  tree  to  tree,  and  at  most  only  from  flower 
to  flower  on  the  same  tree;  and  flowers  on  the  same  tree 
can  be  considered  as  distinct  individuals  only  in  a  limited 
sense.  I  believe  this  objection  to  be  valid,  but  that  nature 
has  largely  provided  against  it  by  giving  to  trees  a  stiong 
tendency  to  bear  flowers  with  separated  sexes.  W  hen  the 
sexes  are  separated,  although  the  male  and  female  floweis 
may  be  produced  on  the  same  tree,  pollen  must  be  regu¬ 
larly  carried  from  flower  to  flower;  and  this  will  give 
a  better  chance  of  pollen  being  occasionally  carried  from 


of  mmviD  uals : 


93 


tree  to  tree.  That  trees  belonging  to  all  orders  have  their 
sexes  more  often  separated  than  other  plants,  I  find  to  be 
the  case  in  this  country;  and  at  my  request  Dr.  Hooker 
tabulated  the  trees  ©f  New  Zealand,  and  Dr.  Asa  Gray, 
those  of  the  United  States,  and  the  result  was  as  I  antici¬ 
pated.  On  the  other  hand.  Dr.  Hooker  informs  me  that 
the  rule  does  not  hold  good  in  Australia:  but  if  most  of 
the  Australian  trees  are  dichogamous,  the  same  result 
would  follow  as  if  they  bore  flowers  with  separated  sexes. 
I  have  made  these  few  remarks  on  trees  simply  to  call 
attention  to  the  subject. 

Turning  for  a  brief  space  to  animals:  various  terrestrial 
species  are  hermaphrodites,  such  as  the  land-mollusca  and 
earth-worms;  but  these  all  pair.  As  yet  I  have  not  found 
a  single  terrestrial  animal  which  can  fertilize  itself.  This 
remarkable  fact,  which  offers  so  strong  a  contrast  with  ter¬ 
restrial  plants,  is  intelligible  on  the  view  of  an  occasional 
cross  being  indispensible;  for  owing  to  the  nature  of  the 
fertilizing  element  there  are  no  means,  analogous  to  the 
action  of  insects  and  of  the  wind  with  plants,  by  which  an 
occasional  cross  could  be  effected  with  terrestrial  animals 
without  the  concurrence  of  two  individuals.  Of  aquatic 
animals,  there  are  many  self-fertilizing  hermaphrodites; 
but  here  the  currents  of  water  offer  an  obvious  means  for 
an  occasional  cross.  As  in  the  case  of  flowers,  I  have  as 
yet  failed,  after  consultation  with  one  of  the  highest 
authorities,  namely.  Professor  Huxley,  to  discover  a  single 
hermaphrodite  animal  with  the  organs  of  reproduction^ 
perfectly  enclosed  that  access  from  without,  and  the  occa¬ 
sional  influence  of  a  distinct  individual,  can  be  shown  to 
be  physically  impossible.  Cirripedes  long  appeared  to  me 
to  present,  under  this  point  of  view,  a  case  of  great  diffi¬ 
culty;  but  I  have  been  enabled,  by  a  fortunate  chance,  to 
prove  that  two  individuals,  though  both  of  self-fertilizing 
hermaphrodites,  do  sometimes  cross. 

It  must  have  struck  most  naturalists  as  a  strange  anomaly 
that,  both  with  animals  and  plants,  some  species  of  the 
same  family  and  even  of  the  same  genus,  though  agreeing 
closely  with  each  other  in  their  whole  organization,  are 
hermaphrodites,  and  some  unisexual.  But  if,  in  fact,  all 
hermaphrodites  do  occasionally  intercross,  the  difference 
between  them  and  unisexual  species  is,  as  far  as  function 
is  concerned,  ver/  siWl. 


94 


CIRCUMSTANCES  FAVORABLE  TO  THE 


From  these  several  considerations  and  from  the  many 
special  facts  which  I  have  collected,  but  which  I  am 
unable  here  to  give,  it  appears  that  with  animals  and 
plants  an  occasional  intercross  between  distinct  individuals 
is  a  very  general,  if  not  universal,  law  of  nature. 

CIRCUMSTANCES  FAVORABLE  FOR  THE  PRODUCTION  OF 
NEW  FORMS  THROUGH  NATURAL  SELECTION. 

This  is  an  extremely  intricate  subject.  A  great  amount 
«4)f  variability,  under  which  term  individual  differences  are 
always  included,  will  evidently  be  favorable.  A  large  num- 
*»ber  of  individuals,  by  giving  a  better  chance  within  any 
given  period  for  the  appearance  of  profitable  variations, 
will  compensate  for  a  lesser  amount  of  variability  in  each 
individual,  and  is,  I  believe,  a  highly  important  element  of 
success.  Though  nature  grants  long  periods  of  time  for 
the  work  of  natural  selection,  she  does  not  grant  an  indefi¬ 
nite  period,  for  as  all  organic  beings  are  striving  to  seize  on 
each  place  in  the  economy  01  nature,  if  any  one  species 
does  not  become  modified  and  improved  in  a  corresponding 
degree  with  its  competitors  it  will  be  exterminated.  U nless 
favorable  variations  be  inherited  by  some  at  least  of  the 
offspring,  nothing  can  be  effected  by  natural  selection. 
The  tendency  to  reversion  may  often  check  or  prevent  the 
work;  but  as  this  tendency  has  not  prevented  man  from 
forming  by  selection  numerous  domestic  races,  why  should 
it  prevail  against  natural  selection? 

In  the  case  of  methodical  selection,  a  breeder  selects  for 
some  definite  object,  and  if  the  individuals  be  allowed  freely 
to  intercross,  his  work  will  completely  fail.  But  when 
many  men,  without  intending  to  alter  the  breed,  have  a 
nearly  common  standard  of  perfection,  and  all  try  to  pro¬ 
cure  and  breed  from  the  best  animals,  improvement  surely 
but  slowly  follows  from  this  unconscious  process  of  selec¬ 
tion,  notwithstanding  that  there  is  no  separation  of  selected 
individuals.  Thus  it  will  be  under  nature;  for  within  a 
confined  area,  with  some  place  in  the  natural  polity  not 
perfectly  occupied,  all  the  individuals  varying  in  the  right 
direction,  though  in  different  degrees,  will  tend  to  be  pre¬ 
served.  But  if  the  area  be  large,  its  several  districts  will 
almost  certainly  present  different  conditions  of  life;  and 


95 


RESULTS  OF  NATURAL  SELECTION. 

then,  if  the  same  species  undergoes  modification  in  differ¬ 
ent  districts,  the  newly  formed  varieties  will  intercross  on 
the  confines  of  each.  But  we  shall  see  in  the  sixth  chap¬ 
ter  that  intermediate  varieties,  inhabiting  intermediate  dis¬ 
tricts,  will  in  the  long  run  generally  be  supplanted  by  one 
of  the  adjoining  varieties.  Intercrossing  will  chiefly  affect 
those  animals  which  unite  for  each  birth  and  wander 
much,  and  which  do  not  breed  at  a  very  quick  rate. 
Hence  with  animals  of  this  nature,  for  instance  birds, 
varieties  will  generally  be  confined  to  separated  countries; 
and.  this  I  find  to  be  the  case.  With  hermaphrodite  or¬ 
ganisms  which  cross  only  occasionally,  and  likewise  with 
animals  which  unite  for  each  birth,  but  which  wander  lit¬ 
tle  and  can  increase  at  a  rapid  rate,  a  new  and  improved 
variety  might  be  quickly  formed  on  any  one  spot,  and 
might  there  maintain  itself  in  a  body  and  afterward 
spread,  so  that  the  individuals  of  the  new  variety  would 
chiefly  cross  together.  On  this  principle  nurserymen 
always  prefer  saving  seed  from  a  large  body  of  plants,  as 
the  chance  of  intercrossing  is  thus  lessened. 

Even  with  animals,  which  unite  for  each  birth,  and  which 
do  not  propagate  rapidly,  we  must  not  assume  that  free  in¬ 
tercrossing  would  always  eliminate  the  effects  of  natural 
selection;  for  I  can  bring  forward  a  considerable  body  of 
facts  showing  that  within  the  same  area  two  varieties  of 
the  same  animal  may  long  remain  distinct,  from  haunting 
different  stations,  from .  breeding  at  slightly  different 
seasons,  or  from  the  individuals  of  each  variety  preferring 
to  pair  together. 

/  Intercrossing  plays  a  very  important  part  in  nature  by 
keeping  the  individuals  of  the  same  species,  or  of  the 
-same  variety,  true  and  uniform  in  character.  It  will 
obviously  thus  act  far  more  efficiently  with  those  animals 
which  unite  for  each  birth;  but,  as  alread}'-  stated,  we 
have  reason  to  believe  that  occesional  intercrosses  take 
place  with  all  animals  and  plants.  Even  if  these  take 
place  only  at  long  intervals  of  time,  the  young  thus  pro¬ 
duced  will  gain  so  much  in  vigor  and  fertility  over  the 
offspring  from  long-continued  self-fertilization,  that  they 
will  have  a  better  chance  of  surviving  and  propagating  their 
kind;  and  thus  in  the  long-run  the  influence  "of  crosses, 
even  at  rare  intervals,  will  be  great.  With  respect  to  or- 


90 


CIRCUMSTANCES  FA  VORABLE  TO  THE 


ganic  beings  extremely  low  in  tlie  scale,  which  do  not 
propagate  sexually,  nor  conjugate,  and  which  cannot  pos¬ 
sibly  intercross,  uniformity  of  character  can  be  retained 
by  them  under  the  same  conditions  of  life,  only  through 
the  principle  of  inheritance,  and  through  natural  selection 
which  will  destroy  any  individuals  departing  from  the 
proper  type.  If  the  conditions  of  life  change  and  the  form 
undergoes  modification,  uniformity  of  character  can  be 
given  to  the  modified  offspring,  solely  by  natural  selection 
preserving  similar  favorable  variations. 
a  Isolation  also  is  an  important  element  in  the  modifica- 
I  tion  of  species  through  natural  selection.  In  a  confined  or 
isolated  area,  if  not  very  large,  the  organic  and  inorganic 
conditions  of  life  will  generally  be  almost  uniform;  so  that 
natural  selection  will  tend  to  modify  all  the  varying  indi¬ 
viduals  of  the  same  species  in  the  same  manner.  Inter¬ 
crossing  with  the  inhabitants  of  the  surrounding  districts, 
will  also  be  thus  prevented.  Moritz  Wagner  has  lately  pub¬ 
lished  an  interesting  essay  on  this  subject,  and  has  sho^n 
that  the  service  rendered  by  isolation  in  preventing  crosses 
between  newly-formed  varieties  is  probably  greater  even  than 
I  supposed.  But  from  reasons  already  assigned  I  can  by  no 
means  agree  with  this  naturalist,  that  migration  and  isola¬ 
tion  are  necessary  elements  for  the  formation  of  new  species. 
The  importance  of  isolation  is  likewise  great  in  prevent¬ 
ing,  after  any  physical  change  in  the  conditions,  such  as 
of  climate,  elevation  of  the  land,  etc.,  the  immigration  of 
better  adapted  organisms ;  and  thus  new  places  in  the 
natural  economy  of  the  district  will  be  left  open  to  be 
filled  up  by  the  modification  of  the  old  inhabitants.  Lastly, 
isolation  will  give  time  for  a  new  variety  to  be  improved  at 
a  slow  rate;  and  this  may  sometimes  be  of  much  import¬ 
ance.  If,  however,  an  isolated  area  be  very  small,  either 
from  being  surrounded  by  barriers,  or  from  having  very 
peculiar  physical  conditions,  the  total  number  of  the  in¬ 
habitants  will  be  small;  and  this  will  retard  the  production 
of  new  species  through  natural  selection,  by  decreasing  the 
chances  of  favorable  variations  arising. 

The  mere  lapse  of  time  by  itself  does  nothing,  either  for 
or  against  natural  selection.  I  state  this  because  it  has 
been  erroneously  asserted  that  the  element  of  time  has 
been  assumed  by  me  to  play  an  all-important  part  in  modi- 


RESULTS  OF  NATURAL  SELECTION.  97 

species,  as  if  all  the  forms  of  life  were  necessarily 
undergoing  change  through  some  innate  law.  Lapse  of 
fime  is  only  so  far  important,  and  its  importance  in  this 
respect  is  great,  that  it  gives  a  better  chance  of  beneficial 
variations  arising  and  of  their  being  selected,  accumulated, 
and  fixed.  It  likewise  tends  to  increase  the  direct  action 
of  the  physical  conditions  of  life,  in  relation  to  the  consti¬ 
tution  of  each  organism. 

If  we  turn  to  nature  to  test  the  truth  of  these  remarks, 
and  look  at  any  small  isolated  area,  such  as  an  oceanic 
island,  although  the  number  of  species  inhabiting  it  is 
small,  as  we  shall  see  in  our  chapter  on  Geographical  Dis¬ 
tribution;  yet  of  these  species  a  very  large  proportion  are 
endemic, — that  is,  have  been  produced  there  and  nowhere 
else  in  the  world.  Hence  an  oceanic  island  at  first  sight 
seems  to  have  been  highly  favorable  for  the  production  of 
new  species.  But  we  may  thus  deceive  ourselves,  for  to 
ascertain  whether  a  small  isolated  area,  or  a  large  open 
area  like  a  continent,  has  been  most  favorable  for  "the  pro¬ 
duction  of  new  organic  forms,  we  ought  to  make  the  com¬ 
parison  within  equal  times;  and  this  we  are  incapable  of 
doing. 

#  Although  isolation  is  of  great  importance  in  the  produc¬ 
tion  of  new  species,  on  the  whole  I  am  inclined  to  believe 
*  that  largeness  of  area  is  still  more  important,  especially  for 
the  production  of  species  which  shall  prove  capable  of 
enduring  for  a  long  period,  and  of  spreading  widely. 

•  Throughout  a  great  and  open  area,  not  only  will  there  be 
I  a  better  chance  of  favorable  variations,  arising  from  the 
I  large  number  of  individuals  of  the  same  species  there  sup- 
|  ported,  but  the  conditions  of  life  are  much  more  complex 
from  the  large  number  of  already  existing  species;  and  if 
some  of  these  many  species  become  modified  and  improved, 
others  will  have  to' be  improved  in  a  corresponding  degree,  or 
they  will  be  exterminated.  Each  new  form,  also,  as  soon  as 
it  has  been  much  improved,  will  be  able  to  spread  over  the 
open  and  continuous  area,  and  will  thus  come  into  competi¬ 
tion  with  many  other  forms.  Moreover,  great  areas,  though 
now  continuous,  will  often,  owing  to  former  oscillations  of 
level,  have  existed  in  a  broken  condition;  so  that  the  good 
effects  of  isolation  will  generally,  to  a  certain  extent,  have 
concurred.  Finally.  I  conclude  that,  although  small 


98  CIRCUMSTANCES  FA  VORABLE  TO  THE 

isolated  areas  have  been  in  some  respects  highly  favorable 
for  the  production  of  new  species,  yet  that  the  course  ot 
modification  will  generally  have  been  more  rapid  on  large 
areas;  and  what  is  more  important,  that  the  new  forms 
produced  on  large  areas,  which  already  have  been  victor¬ 
ious  over  many  competitors,  will  be  those  that  will  spread 
'  most  widely,  and  will  give  rise  to  the  greatest  numbei  of 
new  varieties  and  species.  They  will  thus  play  a  more 
important  part  in  the  changing  history  of  the  oiganic 

world.  .  ..  , 

In  accordance  with  this  view,  we  can,  perhaps,  under¬ 
stand  some  facts  which  will  be  again  alluded  to  m  our 
chapter  on  Geographical  Distribution;  for  instance,  the 
fact  of  the  productions  of  the  smaller  continent  of  Austra¬ 
lia  now  yielding  before  those  of  the  larger  JEuropaso- Asiatic 
area.  Thus,  also,  it  is  that  continental  productions  have 
everywhere  become  so  largely  naturalized  on  islands. 
On  a  small  island,  the  race  for  life  will  have  been  less 
severe,  and  there  will  have  been  less  modification  and  less 
extermination.  Hence,  we  can  understand  how  it  is  that 
the  flora  of  Maderia,  according  to  Oswald  ITeer,  resembles 
to  a  certain  extent  the  extinct  tertiary  flora  of  Hurope. 
All  fresh  water  basins,  taken  together,  make  a  small  aiea 
compared  with  that  of  the  sea  or  of  the  luud. 
sequently,  the  competition  between  freshwater  productions- 
will  have  been  less  severe  than  elsewhere,  new  forms  will 
have  been  then  more  slowly  produced,  and  old  forms  more 
slowly  exterminated.  And  it  is  in  fresh  water  basins  that 
we  find  seven  genera  of  Ganoid  fishes,  remnants  of  a  once 
preponderant  order :  and  in  fresh  water  we  find  some  of  the 
most  anomalous  forms  now  known  in  the  world  as  the 
Ornithorhynchus  and  Lepidosiren,  which,  like  fossils,  con¬ 
nect  to  a  certain  extent  orders  at  present  widely  sundered 
in  the  natural  scale.  These  anomalous  forms  may  be 
called  living  fossils;  they  have  endured  to  the  present  day, 
from  having  inhabited  a  confined  area,  and  from  having 
been  exposed  to  less  varied,  and  therefore  less  severe,  com- 

To  sum  up,  as  far  as  the  extreme  intricacy  of  the  subject 
permits,  the  circumstances  favorable  and  unfavorable  for 
\  the  production  of  new  species  through  natural  selection. 

\  1  conclude  that  for  terrestrial  productions  a  large  contx- 


RESULTS  OF  NATURAL  SELECTION.  99 

nexital  area,  which  has  undergone  many  oscillations  of 
level,  will  have  been  the  most  favorable  for  the  production 
of  many  new  forms  of  life,  fitted  to  endure  for  a  Ions’  time 
and  to  spread  widely.  While  the  area  existed  as  a' conti¬ 
nent  the  inhabitants. will  have  been  numerous  in  individu¬ 
als  and  kinds,  and  will  have  been  subjected  to  severe  com¬ 
petition.  .  \\  hen  converted  by  subsistance  into  large 
separate  islands  there  will  still  have  existed  many  indi¬ 
viduals  of  the  same  species  on  each  island:  intercrossing 
on  the  confines  of  the  range  of  each  new  species  will  have 
been  checked:  after  physical  changes  of  any  kind  immigra- 
tion  wdl  have  been  prevented,  so  that  new  places  in  the 
polity  of  each  island  wifi  have  had  to  be  filled  up  by  the 
modification  of  the  old  inhabitants;  and  time  will  have 
been  allowed  for  the  varieties  in  each  to  become  well  modi¬ 
fied  and  perfected.  When,  by  renewed  elevation,  the 
islands  were  reconverted  into  a  continental  area,  there  will 
again  have  been  very  severe  competition;  the  most  favored 
or  improved  varieties  will  have  been  enabled  to  spread* 
there  will  have  been  much  extinction  of  the  less  improved 
l°i’fs  and  the  relative  proportional  numbers  of  the  various 
inhabitants  of  the  reunited  continent  will  again  have  been 
changed;  and  again  there  will  have  been  a  fair  field  for 
natural  selection  to  improve  still  further  the  inhabitants 
and  thus  to  produce  new  species. 

^-^4?  r^ural  selection  generally  acts  with  extreme  slow¬ 
ness  1  fully  admit.  It  can  act  only  when  there  are  places 
u}  the  natural  polity  of  a  district  which  can  be  better  occu¬ 
pied  by  the  modification  of  some  of  its  existing  inhabitants. 
Ifiq  occurrence  of  such  places  will  often  depend  on  physi- 
cal  changes,  which  generally  take  place  very  slowly,  and 
on  the  immigration  of  better  adapted  forms  being  pre- 

^ some  ^ew  ^ke  old  inhabitants  become  modi¬ 
fied  the  mutual  relations  of  others  will  often  be  disturbed* 
and  this  will  create  new  places,  ready  to  be  filled  up  by 
better  adapted  forms;  but  all  this  will  take  place  very 
Although  all  the  individuals  of  the  same  species 
difler  m  some  slight  degree  from  each  other,  it  would  often 
be  long  befyre  differences  of  the  right  nature  in  various 
parts  of  the  organization  might  occur.  The  result  would 
°tt*  greatly  retarded  by  free  intercrossing.  Many  will 
excj  aim  that  these  several  causes  are  amply  sufficient  to 


100  EXTINCTION  BT  NATURAL  SELECITON. 

neutralize  the  power  of  natural  selection.  _  I  do  not  believe 
so  But  I  do  believe  that  natural  selection  will  generally 
act  very  slowly,  only  at  long  intervals  of  time,  and  only  on 
a  few  of  the  inhabitants  of  the  same  region.  I  further 
believe  that  these  slow,  intermittant  results  accord  well 
with  what  geology  tells  us  of  the  rate  and  manner  at  which 
the  inhabitants  of  the  world  have  changed. 

Slow  though  the  process  of  selection  may  be,  if  feeble 
man  can  do  much  by  artificial  selection,  I  can  see  no  limit 
to  the  amount  of  change,  to  the  beauty  and  complexity  of 
the  coadaptations  between  all  organic  beings,  one  with 
another  and  with  their  physical  conditions  of  life,  which 
may  have  been  affected  in  the  long  course  of  time  through 
nature’s  power  of  selection,  that  is  by  the  survival  of  the 
fittest. 

EXTINCTION  CAUSED  BY  NATURAL  SELECTION. 

This  subject  will  be  more  fully  discussed  in  our  chap¬ 
ter  on  Geology;  but  it  must  here  be  alluded  to  from 
being  intimately  connected  with  natural  selection.  Nat¬ 
ural  selection  acts  solely  through  the  preservation  of  vari¬ 
ations  in  some  way  advantageous,  which  consequently  en¬ 
dure  Owing  to  the  high  geometrical  rate  of  inciease  of 
all  organic  beings,  each  area  is  already  fully  stocked  with 
inhabitants;  and  it  follows  from  this,  that  as  the  favored 
forms  increase  in  number,  so,  generally,  will  the  less  fa¬ 
vored  decrease  and  become  rare.  Rarity,  as  geology  tells 
us,  is  the  precursor  to  extinction.  We  can  see  that  any 
form  which  is  represented  by  few  individuals  will  run  a 
(rood  chance  of  utter  extinction,  during  great  fluctuations 
m  the  nature  or  the  seasons,  or  from  a  temporary  increase 
ir  the  number  of  its  enemies.  But  we  may  go  further  than 
this"  for,  as  new  forms  are  produced,  unless  we  admit  that 
specific  forms  can  go  cn  indefinitely  increasing  in  number, 
many  old  forms  must  become  extinct.  That  the  number 
of  specific  forms  has  not  indefinitely  increased,  geology 
plainly  tells  us;  and  we  shall  presently  attempt  to  show 
why  it  is  that  the  number  of  species  throughout  the  world 
has  not  become  immeasurably  gi  eat.  . 

We  have  seen  that  the  species  which  are  most  numer¬ 
ous  in  individuals  have  the  best  chance  of  producing  favor- 


DIVERGENCE  OF  CHARACTER.  lw 

able  variations  within  any  given  period.  We  have  evi¬ 
dence  of  this,  m  the  facts  stated  in  the  second  chapter 

®k”j,ng  18  l w  common  and  diffused  or  dominant 

species  which  offer  the  greatest  number  of  recorded  vari¬ 
eties.  Hence, _  rare  species  will  be  less  quickly  modified  or 
improved  within  any  given  period;  they  will  consequently 
be  beaten  in  the  race  for  life  by  the  modified  and  improved 
descendants  of.  the  commoner  species. 

Prom  these  several  considerations  I  think  it  inevitably 
follows,  that  as  new  species  in  the  course  of  time  are 
formed  through  natural  selection,  others  will  become  rarer 
and  rarer,  and  finally  extinct.  The  forms  which  stand  in 
closest  competition  with  those  undergoing  modification 
and  improvement,  will  naturally  suffer  most.  And  we 
have  seen  in  the  chapter  on  the  Struggle  for  Existence 
that  it  is  the  most  closely-allied  forms,— varieties  of  the 
same  species,  and  species  of  the  same  genus  or  related 

from  ha^ng  nearly  the  same  structure, 
constitution  and  habits,  generally  come  into  the  severest 
competition  with  each  other  consequently,  each  new  vari¬ 
ety  or  species,  during  the  progress  of  its  formation,  will 
generally  press  hardest  on  its  nearest  kindred,  and  tend  to 
exterminate  them.  We  see  the  same  process  of  extermina¬ 
tion  among _  our  domesticated  productions,  through  the 
selection  of  improved  forms  by  man.  Many  curious  in¬ 
stances  could  be  given  showing  how  quickly  new  breeds  of 
cattle,  sheep  and  other  animals,  and  varieties  of  flowers 
take  the  place  of  older  and  inferior  kinds.  In  Yorkshire’ 
it  is  historically  known  that  the  ancient  black  cattle  were 
displaced  by  the  long-horns,  and  that  these  “  were  swept 

t,3  by-ftht  s“rns  ”  (I  <ll,ote  the  vvorcls  <>f  »»  agricul- 
tuial  wnter)  as  if  by  some  murderous  pestilence.” 

divergence  of  character. 

yhe  principle,  which  I  have  designated  by  this  term,  is 
importance,  and  explains,  as  I  believe,  several  im¬ 
portant  facts.  In  the  first  place,  varieties,  even  strongly 
marked  ones,  though  having  somewhat  of  the  charac- 
ter  of  species— as  is  shown  by  the  hopeless  doubts 

many  cases  how  to  rank  them— yet  certainly  differ 
m  less  from  each  other  than  do  good  and  distinct 


DIVERGENCE  OF  CHARACTER . 


102 

species.  Nevertheless  according  to  my  view,  varieties  are 
species  in  the  process  of  formation,  or  are,  as  I  have  called 
them,  incipient  species.  How,  then,  does  the  lesser  differ¬ 
ence  between  varieties  become  augmented  into  the  greater 
difference  between  species?  I  hat  this  does  habitually 
happen,  we  must  infer  from  most  of  the  innumerable 
species  throughout  nature  presenting  well-marked  differ¬ 
ences;  whereas  varieties,  the  supposed  prototypes  and 
parents  of  future  well-marked  species,  present  slight  and 
ill-defined  differences.  Mere  chance,  as  we  may  call  it, 
might  cause  one  variety  to  differ  in  some  character  from  its 
parents,  and  the  offspring  of  this  variety  again  to  differ 
from  its  parent  in  the  very  same  character  and  in  a  greater 
degree;  but  this  alone  would  never  account  for  so  habitual 
and  large  a  degree  of  difference  as  that  between  the  species 
of  the  same  genus. 

As  has  always  been  my  practice,  I  have  sought  light  on 
this  head  from  our  domestic  productions.  We  shall  here 
find  something  analogous.  It  will  be  admitted  that  the 
production  of  races  so  different  as  short-horn  and  Here¬ 
ford  cattle,  race  and  cart  horses,  the  several  breeds  of 
pigeons,  etc.,  could  never  have  been  effected  by  the  mere 
chance  accumulation  of  similar  variations  during  many 
successive  generations.  In  practice,  a  fancier  is,  foi  in¬ 
stance,  struck  by  a  pigeon  having  a  slightly  shorter  beak; 
another  fancier  is  struck  by  a  pigeon  having  a  rather  longer 
beak;  and  on  the  acknowledged  principle  that  “  fanciers 
do  not  and  will  not  admire  a  medium  standard,  but  like 
extremes,”  they  both  go  on  (as  has  actually  occurred  with 
the  sub-breeds  of  the  tumbler-pigeon)  choosing  and  breed¬ 
ing  from  birds  with  longer  and  longer  beaks,  or  with 
shorter  and  shorter  beaks.  Again,  we  may  suppose  that 
at  an  early  period  of  history,  the  men  of  one  nation  or  dis¬ 
trict  required  swifter  horses,  while  those  of  another  re¬ 
quired  stronger  and  bulkier  horses.  The  early  differences 
would  be  very  slight;  but,  in  the  course  of  time,  from  the 
continued  selection  of  swifter  horses  in  the  one  case,  and 
of  stronger  ones  in  the  other,  the  differences  would  become 
greater,  and  would  be  noted  as  forming  two  sub-breeds. 
Ultimately  after  the  lapse  of  centuries,  these  s-ub-breeds 
would  become  converted  into  two  well-established  and  dis¬ 
tinct  breeds.  As  the  differences  became  greater,  the  in- 


DIVERGENCE  OF  CHARACTER.  103 

ferior  animals  with  intermediate  characters,  being  neither 
very  swift  nor  very  strong,  would  not  have  been  used  for 
breeding,  and  will  thus  have  tended  to  disappear.  Here, 
then,  we  see  in  man  s  productions  the  action  of  what  may  bei 
called  the  principle  of  divergence,  causing  differences,  at! 
first  barely  appreciable,  steadily  to  increase,  and  the  breeds 
to  diverge  in  character,  both  from  each  other  and  from 
their  common  parent. 

But,  how,  it  may  be  asked,  can  any  analogous  principle 
apply  in  nature?  I  believe  it  can  and  does  apply  most 
efficiently  (though  it  was  a  long  time  before  I  saw  how), 
from  the  simple  circumstance  that  the  more  diversified  the 
descendants  from  any  one  species  become  in  structure, 
constitution  and  habits,  by  so  much  will  they  be  better 
enabled  to  seize  on  many  and  widely  diversified  places  in 

the  polity  of  nature,  and  so  be  enabled  to  increase  in 
numbers. 

.  We  can  clearly  discern  this  in  the  case  of  animals  with 
simple  habits.  Take  the  case  of  a  carnivorous  quadruped, 
of  which  the  number  that  can  be  supported  in  any  country 
has  long  ago  arrived  at  its  full  average.  If  its  natural 
power  of  increase  be  allowed  to  act,  it  can  succeed  in  in¬ 
creasing  (the  country  not  undergoing  any  change  in  con¬ 
ditions)  only  by  its  varying  descendants  seizing  on  places 
at  present  occupied  by  other  animals:  some  of  them,  for 
instance,  being  enabled  to  feed  on  new  kinds  of  prey, 
either  dead  or  alive;  some  inhabiting  new  stations,  climb¬ 
ing  trees,  frequenting  water,  and  some  perhaps  becoming 
less  carnivorous.  The  more  diversified  in  habits  and 
structure  the  descendants  of  our  carnivorous  animals 
become,  the  more  places  they  will  be  enabled  to  occupy. 
What  applies  to  one  animal  will  apply  throughout  all  time 
to  all  animals — that  is,  if  they  vary — for  otherwise  natural 
selection  can  effect  nothing.  So  it  will  be  with  plants.  It 
has  been  experimentally  proved,  that  if  a  plot  of  ground 
be  sown  with  one  species  of  grass,  and  a  similar  plot  be 
sown  with  several  distinct  genera  of  grasses,  a  greater 
number  of  plants  and  a  greater  weight  of  dry  herbage  can 
be  raised  in  the  latter  than  the  former  case.  The  same  has 
been  found  to  hold  good  when  one  variety  and  several  mixed 
varieties  of  wheat  have  been  sown  on  equal  spaces  of 
ground.  Hence,  if  any  one  species  of  grass  were  to  go  on 


104 


DIVERGENCE  OF  CHARACTER. 


varying,  and  the  varieties  were  continually  selected  which 
differed  from  each  other  in  the  same  manner,  though  in  a 
very  slight  degree,  as  do  the  distinct  species  and  genera  of 
grasses,  a  greater  number  of  individual  plants  of  this 
species,  including  its  modified  descendants,  would  succeed 
in  living  on  the  same  piece  of  ground.  And  we  know  that 
each  species  and  each  variety  of  grass  is  annually  sowing 
almost  countless  seeds;  and  is  thus  striving,  as  it  may  be 
said,  to  the  utmost  to  increase  in  number.  Consequently, 
in  the  course  of  many  thousand  generations,  the  most  dis¬ 
tinct  varieties  of  any  one  species  of  grass  would  have  the 
best  chance  of  succeeding  and  of  increasing  in  numbers, 
and  thus  of  supplanting  the  less  distinct  varieties;  and 
varieties,  when  rendered  very  distinct  from  each  other, 
take  the  rank  of  species. 

The  truth  of  the  principle  that  the  greatest  amount  of 
life  can  be  supported  by  great  diversification  of  structure, 
is  seen  under  many  natural  circumstances.  In  an  extremely 
small  area,  especially  if  freely  open  to  immigration,  and 
^diere  the  contest  between  individual  and  individual  must 
be  very  severe,  we  always  find  great  diversity  in  its  inhabi¬ 
tants.  For  instance,  I  found  that  a  piece  of  turf,  three 
feet  by  four  in  size,  which  had  been  exposed  for  many 
years  to  exactly  the  same  conditions,  supported  twenty 
species  of  plants,  and  these  belonged  to  eighteen  genera 
and  to  eight  orders,  which  shows  how  much  these  plants 
.differed  from  each  other.  So  it  is  with  the  plants  and 
insects  on  small  and  uniform  islets:  also  in  small  ponds  of 
fresh  water.  Farmers  find  that  they  can  raise  more  food 
by  a  rotation  of  plants  belonging  to  the  most  different 
orders:  nature  follows  what  may  be  called  a  simultaneous 
rotation.  Most  of  the  animals  and  plants  which  live  close 
round  any  small  piece  of  ground,  could  live  on  it  (suppos¬ 
ing  its  nature  not  to  be  in  any  way  peculiar),  and  may  be 
said  to  be  striving  to  the  utmost  to  live  there;  but,  it  is 
seen,  that  where  they  come  into  the  closest  competition,  the 
advantages  of  diversification  of  structure,  with  the  accom¬ 
panying  differences  of  habit  and  constitution,  determine 
that  the  inhabitants,  which  thus  jostle  each  other  most 
closely,  shall,  as  a  general  rule,  belong  to  what  we  call 
different  genera  and  orders. 

The  same  principle  is  seen  in  the  naturalization  of 


D IV Ell G ENGE  OF  G1IA  UA GTER.  >  q  ~ 

plants  through  man’s  agency  in  foreign  lands  It  might 
Imve  been  expected  that  the  plants  which  would  uc- 
ceed  in  becoming  naturalized  in  any  land  would  generally 
have  been  closely  allied  to  the  indigenes;  for  these  ! 

“wKuntv  atTtaS  Created  “d  adaP‘«d  for 

nected ^  that  n^tLv1  u“,g,ht  .als0’  PerhaPs-  have  been  ex- 
pccted  that  natuialized  plants  would  have  belonged  to  a 

thlifnew8  h1o0meeseSPBlat11Hadapted  -to  certain  sta‘ions  in 
eir  new  homes.  But  the  case  is  very  different-  ami 

Alph.  de  Candolle  has  well  remarked,  in  his  great  ami 

p  rt'ioi  allv  n!lat  floras  g‘T  by  naturalfzafion^  prl 
poi tionally  with  the  number  of  the  native  genera  ami 

species,  far  more  in  new  genera  than  in  new  species  To 

give  a  single  instance:  in  the  last  edition  of  Dr  PAsa  Grav’s 

Manual  of  the  Flora  of  the  Northern  United  States ’’  2G0 

natuialized  plants  are  enumerated,  and  these  belong-  to  TG2 

genera  We  thus  see  that  these  natu  rai  zed  pal  are  of 

a  highly  diversified  nature.  They  differ  moreover  to  f 

arge  extent,  from  the  indigenes,  for  out  of  the  ]  62 

LlSous  fnd6^  n°  ',eSS  thau  100  ^era  a«  not  there 
to  tlfo  ’  d  th,“sa  lai'ge  proportional  addition  is  made 
to  the  genera  now  hving  in  the  United  States. 

By  considenng  the  nature  of  the  plants  or  animals  which 
have  m  any  country  struggled  successfully  with  the  indi- 
f®"es’  a",f  laV°  there  become  naturalized,  we  may  gain 
0In®,  cTru(^e  lf^ea  in  what  manner  some  of  the  natfvp^ 

o7eftheDecompatZf fi6d  1  ^  to  gain  an  “dvantege 

diversification  ofP  strnct;  a"d  W®  m?y  at  least  infer  thit  1 
uiveisincation  ot  structure,  amounting  to  new  generic  d if  ' 

ferences,  would  be  profitable  to  them.  §  / 

inhabitandtsaoftatghe  same  reg^Ts^M  fait  “  tfhe 

of  the  physiological  dTvSIl'ta  W  nil ^  oi-ZsoVhe 

Mihie  Edwards  ?l]b^Ct  S0  well  elSatl  by 

.N°  Physiologist  doubts  that  a  stomach 
adapted  to  digest  vegetable  matter  alone  or  flesh  Xne 

d“°St  nu"triment  from  these  substances.  So  h!  the 

eapableof  there  sulVoidifnilmseuls?1’  A  sefoflnfmals® 
with  their  organization  but  little  diversified,  could  hardly 


106 


RESULT  OF  THE  ACTION 


compete  with  a  set  more  perfectly  le  Austahan 

It  may  be  doubted,  for  instance,  whether  the  Australian 

mammals  which  are  divided  into  groups  differing  but 
little  from  each  other,  and  feebly  representing,  as  Mr. 
Waterhouse  and  others  have  remarked,  our  carnivoious, 
ruminant  and  rodent  mammals,  could  Buccessfully  com¬ 
pete  with  these  well -developed  orders.  In  the  Australian 
mammals,  we  see  the  process  of  diversification  in  an  eaily 
and  incomplete  stage  of  development. 


the  probable  effects  of  the  ACTI0^p0Fr//RT^ 

SELECTION  THROUGH  DIVERGENCE  OP ' 

and  extinction,  on  the  descendants  of  a  com¬ 
mon  ANCESTOR. 


After  the  foregoing  discussion,  which  has  been  much 
compressed,  we  may  Lame  that  the  modified  descendants 
of  any  one  species  will  succeed  so  much  the  better  as  tl  ey 
become  more1  diversified  in  structure  and  axe thus .enabled 
to  encroach  on  places  occupied  by  other  beings.  Now  let 
us  see  how  thif  principle  "of  benefit  being  derived  from 
divergence  of  character,  combined  with  the  pnnciples  ol 
natural  selection  and  of  extinction,  tends  to  act.  ,. 

The  accompanying  diagram  will  aid  us  m  understanding 
this  rather  perplexing  subject.  Let  A  to  L  represent  the 
species  of  a  genus  large  in  its  own  country;  these  species  are 
supposed  to°resemble  each  other  in  unequal  degrees,  as  is 
so  generally  the  case  in  nature,  and  as  is  represented 
in  the  diagram  by  the  letters  standing  at  unequal  distances. 

I  have  said  a  la,|e  genus,  because  as  we  saw  in  the  second 
chapter,  on  an  average  more  species  vary  in  larg  g 
than  in  small  genera;  and  the  varying  species  of  the  huge 
p-enera  present  a  greater  number  of  varieties.  \Ve  hav  , 
flso,  seen  that  the  species,  which  are  the  commonest  and 
most  widely  diffused,  vary  more  than  do  the  raie  ana 
restricted  species.  Let  (A)  be  a  common,  widelj-diffused, 
and  varying  species,  belonging  to  a  genus  large  .  { 

country.  The  branching  and  diverging  dotted  lines  ol 
unequal  lengths  proceeding  from  (A),  may  represent  its 
offspring.  The  variations  are  supposed  to  be 
Sttemely  shfht,  but  of  the  most  diversified  nature;  they 
are  not  Supposed  all  to  appear  simultaneously,  but  often 


OF  NATURAL  SELECTION.  107 

after  long  intervals  of  time;  nor  are  they  all  supposed  to 
endure  for  equal  periods.  Only  those  variations  which  are 
m  some  way  profitable  will  be  preserved  or  naturally 
selected.  And  here  the  importance  of  the  principle  of 
benefit  derived  from  divergence  of  character  comes  in:  for 
this  will  generally  lead  to  the  most  different  or  divergent 
variations  (represented  by  the  outer  dotted  lines)  beino- 
preserved  and  accumulated  by  natural  selection.  When  a 
dotted  line  reaches  one  of  the  horizontal  lines,  and  is  there 
marked  by  a  small  numbered  letter,  a  sufficient  amount  of 
vaiiation  is  supposed  to  have  been  accumulated  to  form  it 
into  a  fairly  well  marked  variety,  such  as  would  be  thought 
worthy  of  record  m  a  systematic  work. 

The  intervals  between  the  horizontal  lines  in  the  dia¬ 
gram,  may  represent  each  a  thousand  or  more  generations. 
Atter  a  thousand  generations,  species  (A)  is  supposed  to 
have  produced  two  fairly  well  marked  varieties,  namely 
a  and  m  These  two  varieties  will  generally  still  be 
exposed  to  the  same  conditions  which  made  their  parents 
variable,  and  the  tendency  to  variability  is  in  itself  hered¬ 
itary;  consequently  they  will  likewise  tend  to  vary,  and 
commonly  m  nearly  the. same  manner  as  did  their  parents. 
Moreover  these  two  varieties,  being  only  slightly  modified 

inis,  will  tend  to  inherit  those  advantages  which  made 
their  parent  (A)  more  numerous  than  most  of  the  other 
inhabitants  of  the  same  country;  they  will  also  partake  of 
tnqse  more  general  advantages  which  made  the  genus  to 
which  the  parent  species  belonged,  a  large  genus  in  its  own 
country.  And  all  these  circumstances  are  favorable  to  the 
production  of  new  varieties. 

If,  then  these  two  varieties  be  variable,  the  most 
divergent  of  their  variations  will  generally  be  preserved 
during  the  next  thousand  generations.  And  after  this 
interval,  variety  a  is  supposed  in  the  diagram  to  have  pro¬ 
duced  variety  a2,  which  will,  owing  to  the  principle  of 
divergence  differ  more  from  (A)  than  did  variety  a1. 
Variety  m  is  supposed  to  have  produced  two  varieties, 
namely  m  and  5 2  differing  from  each  other,  and  more 
considerably  from  their  common  parent  (A).  We  may 
continue  the  process  by  similar  steps  for  any  length  of 
ime;  some  of  the  varieties,  after  each  thousand  genera¬ 
tions,  producing  only  a  single  variety,  but  in  a  more  and 


108 


RESULT  OF  THE  ACTION 


o“  V14 

bJ  4  f1* 

—r" 

fl  ... - •  - — ...  ■  ■— — 

\  •; 

\ 

« 

«  • 

i 

9 

\  •  t 

\  •  i 

\  i 

%  • 

\  ! 

t 

# 

t 

\  •  • 

1  1  . 

%  t 

t 

v  !  / 

- i  jr 

1  •  ' 

%  •  / 

\ 

1  t  / 

\  J  / 

\  /  * 

\ i  A 

%  •  / 

\  / 

\  :  7 

\  |  / 

%  1  #. 

\  1  #  • 

•  t 

\  !  /  — 

«J0 

mS° 

vw 

\  J  // 

\  !  / 

\  / 

\  l 

aF'tyT 

\!//*  - 

\  ..  !  / 

\  I  / 

\  1 

•  V 

- - - - 

1° 

Cl/ 


\  f 
\  :  .• 
t  *v\ !  / 


\\  /  / 


\!  ns 

__4 - 


\  i . 

-Sul7 


cU 


\  l 
\ :  . 
6  ;// 


1L 1 


\  ! 

\i*' 


j  -*  771/ 


\  S  \  f 

a's  --W 


k*y 


ar 


\  i  / 


\  \i  / 
\  *•' , 

-f 


••  •'  i  .  J 


\  i  / 


a? '%> 


Hi/  \!,4 

t:  JJ  •.'■/■■■  a 

rv:  1/  \y.-  771/ 


,  ,7 

\  / 

\  •  / 


:  / 


\  :  i 

\  \  :  •• 

A\:  / 


if/ 

l  •'/  -2 

\&  TYV 


■  "v' 


A  B 


D 


E 


% 

% 


% 

\ 


i 

I 

% 

« 

• 

1 

% 


\ 


I 

9 

f 

i 

$ 

A 


$ 

# 

• 

t 

t 


* 


t 


I 


OF  NATURAL  SELECTION. 


109 


XIV 


.XIII 


110 


RESULT  OF  THE  ACTION 


more  modified  condition,  some  producing  two  or  three 
varieties,  and  some  failing  to  produce  any.  Ihus  the 
varieties  or  modified  descendants  of  the  common  parent 
m  will  generally  go  on  increasing  m  number  and  diverg¬ 
ing ’in  character.  In  the  diagram  the  process  is  repre¬ 
sented  up  to  the  ten-thousandth  generation,  and  under  a 
condensed  and  simplified  form  up  to  the  fourteen-thous- 

andtli  generation.  a-l  j. 

But  1  must  here  remark  that  I  do  not  suppose  that  the 
process  ever  goes  on  so  regularly  as  is  represented  m  the 
diagram,  though  in  itself  made  somewhat  irregular  nor 
that  it  goes  on  continuously;  it  is  far  more  probable  that 
each  form  remains  for  long  periods  unaltered,  and  then 
again  undergoes  modification.  Nor  do  I  suppose  that  the 
most  divergent  varieties  are  invariably  preserved :  a  medium 
form  may  often  long  endure,  and  may  or  may  not  produce 
more  than  one  modified  descendant;  for  natural  selection 
will  always  act  according  to  the  nature  of  the  places  which 
are  either  unoccupied  or  not  perfectly  occupied  by  other 
beings;  and  this  will  depend  on  infinitely  complex  rela¬ 
tions  But  as  a  general  rule,  the  more  diversified  m  struc¬ 
ture  the  descendants  from  any  one  species  can  be  rendered, 
the  more  places  they  will  be  enabled  to  seize  on,  and  the 
more  their  modified  progeny  will  increase..  In  our  diagram 
the  line  of  succession  is  broken  at  regular  intervals  by  small 
numbered  letters  marking  the  successive  forms  which  have 
become  sufficiently  distinct  to  be  recorded  as  varieties.  But 
these  breaks  are  imaginary,  and  might  have  been  mserte 
anvwhere,  after  intervals  long  enough  to  allow  the  accumu¬ 
lation  of  a  considerable  amount  of  divergent  variation. 

As  all  the  modified  descendents  from  a  common  and 
■widely-diffused  species,  belonging  to  a  large  genus,  will 
tend  to  partake  of  the  same  advantages  which  made  their 
parent  successful  in  life,  they  will  generally  go  on  multi¬ 
plying  in  number  as  well  as  diverging  m  character  this 
is  represented  in  the  diagram  by  the  several  divergent 
branches  proceeding  from  (A)..  The  modified  offspring 
from  the  later  and  more  highly  improved  branches  m  the 
lines  of  descent,  will,  it  is  probable,  often  take  the  place 
of  and  so  destrov,  the  earlier  and  less  improved  branches: 
this  is  represented  in  the  diagram  by  some  of  the  lower 
branches  not  reaching  to  the  upper  horizontal  lines,  in 


OF  NATURAL  SELECTION . 


Ill 


some  cases  no  doubt  the  process  of  modification  will  be 
confined  to  a  single  line  of  descent,  and  the  number  of 
modified  descendants  will  not  be  increased;  although  the 
amount  of  divergent  modification  may  have  been  augmented. 
This  case  would  be  represented  in  the  diagram,  if  all  the 
lines  proceeding  from  (A)  were  removed,  excepting  that 
f  1  om  to  ai0.  In  the  same  way  the  English  racehorse 
and  English  pointer  have  apparently  both  gone  on  slowly 
diverging  in  character  from  their  original  stocks,  without 
either  having  given  off  any  fresh  branches  or  races. 

After  ten  thousand  generations,  species  (A)  is  supposed 
to  have  produced  three  forms,  and  m10,  which, 

from  having  diverged  in  character  during  the  successive 
generations,  will  have  come  to  differ  largely,  but  perhaps 
unequally,  from  each  other  and  from  their  common  parent. 
If  we  suppose  the  amount  of  change  between  each  hori¬ 
zontal  line  in  our  diagram  to  be  excessively  small,  these 
three  forms  may  still  be  only  well-marked  varieties;  but 
we  have  only  to  suppose  the  steps  in  the  process  of  modi¬ 
fication  to  be  more  numerous  or  greater  in  amount,  to 
convert  these  three  forms  into  doubtful  or  at  least  into 
well-defined  species.  Thus  the  diagram  illustrates  the 
steps  by  which  the  small  differences  distinguishing  varieties 
are  increased  into  the  larger  differences  distinguishing 
species.  By  continuing  the  same  process  for  a  greater 
number  of  generations  (as  shown  in  the  diagram  in  "a  con¬ 
densed  and  simplified  manner),  we  get  eight  species,  marked 
by  the  letters  between  a14  and  m14,  all  descended  from 
(A).  Thus,  as  I  believe,  species  are  multiplied  and  genera 
are  formed. 

.  a  large  genus  it  is  probable  that  more  than  one  spe¬ 
cies  would  vary.  In  the  diagram  I  have  assumed  that  a 
second  species  (I)  has  produced,  by  analogous  steps,  after 
ten  thousand  generations,  either  two  well-marked  varieties 
(w10  and  z10)  or  two  species,  according  to  the  amount  of 
change  supposed  to  be  represented  between  the  horizontal 
lines.  After  fourteen  thousand  generations,  six  new  spe¬ 
cies,  marked  by  the  letters  n14  to  z14,  are  supposed  to 
have  been  produced.  In  any  genus,  the  species  which  are 
already  very  different  in  character  from  each  other,  will 
generally  tend  to  produce  the  greatest  number  of  modified 
descendants;  for  these  will  have  the  best  chance  of  seizing 


112  RESULT  OF  THE  ACTION 

or  new  and  widely  different  places  in  the  polity  of  nature; 
hence  in  the  diagram  I  have  chosen  the  extreme  species 
(  \  i  and  the  nearly  extreme  species  (I),  as  those  whicl 
have  largely  varied,  and  have  given  rise  to  new  varieties 
and  suedes  The  other  nine  species  (marked  by  capital 
fotteXTour  original  genus,  may  for  long  but  unequal 
neriods  continue  to  transmit  unaltered  descendants,  and 
this  is  shown  in  the  diagram  by  the  dotted  lines  unequa  y 

FSEto,;i’g“«  process  oi  „oai«c,ti.n  rep^cntoi  » 

fully  stocked  country  natural  selection  necessari  y  ac  s  j 
l  he  selected  form  having  some  advantage  in  the  snuggle 
for  life  oter  other  forms,  there  will  be  a  constant  tendency 
in  the  improved  descendants  of  anyone  species  to  supplant 
and  Exterminate  in  each  stage  of  descentUen-pi^ece^o^ 
and  their  original  progenitor.  For  it  s  ion  Id  be: r< ame 
bered  that  the  competition  will  geneially  be  most  seveie 
between  those  forms  which  are  most  nearly  related  to  each 
other  in  habits,  constitution  and  structure.  Hence  all  th 
intermediate  forms  between  the  earlier  and  latei  states, 
that  is  between  the  less  and  more  unproved  states  of 
the  same  species,  as  well  as  the  original  parent  specms 
itself  will  generally  tend  to  become  extinct,  bo  it  pioba 
blv  will  be  with  many  whole  collateral  lines  of  descent, 
winch  will  be  conquered  by  later  and  improved  lines.  , 

however,  the  modified  offspring  of  a  .  cieS^g®ft 
some  distinct  country,  or  become  quickly  adapted  to 
son  e  quite  new  station,  in  which  offspring  and  progen¬ 
itor  do  not  come  into  competition,  both  may  continue  to 

eXTf'  then  our  diagram  be  assumed  to  represent  a  consid¬ 
erable*  amount  of  modification,  species  (A)  and  all  the 
earlier  varieties  will  have  become  extinct,  being  1  enlaced  b) 
eight  new  species  («“  to  and  species  (I)  will  be  le- 

reared  bv  six  (nu  to  zu)  new  species.  .  .  1  , 

1  But  we  may  go  further  than  this.  The  original  species  of 

our  genus  were  supposed  to  resemble  each  other  m  unequal 

degrees  as  is  so  generally  the  case  in  nature;  species  (  A)  being 

more  nearly  related  to  B,  C  and  D  than  to  the  other  spe¬ 
cies;  and  species  (I)  more  to  G,  H,  K,  L  than  to  the  o  iei  - 


OF  NATURAL  SELECTION. 


11? 


These  two  species  (A  and  I)  were  also  supposed  to  be  very 
coni  m  on  and  widely  diffused  species,  so  that  they  must 
originally  have  had  some  advantage  over  most  of  the  other 
species  of  the  genus.  Their  modified  descendants,  four¬ 
teen  in  number  at  the  fourteen-thousandth  generation,  will 
probably  have  inherited  some  of  the  same  advantages; 
they  have  also  been  modified  and  improved  in  a  diversified 
manner  at  each  stage  of  descent,  so  as  to  have  become 
adapted  to  many  related  places  in  the  natural  economy  of 
their  country.  It  seems,  therefore,  extremely  probable  that 
they  will  have  taken  the  places  of,  and  thus  exterminated, 
not  only  their  parents.  (A)  and  (I),  but  likewise  some  of 
the  original  species  which  were  most  nearly  related  to  their 
parents.  Hence  very  few  of  the  original  species  will  have 
transmitted  offspring  to  the  fourteenth  thousandth  genera¬ 
tion..  We  may  suppose  that  only  one  (F)  of  the  two 
species  (E  and  F)  which  were  least  closely  related  to  the 
other  nine  original  species,  has  transmitted  descendants  to 
this  late  stage  of  descent. 

The  new  species  in  our  diagram,  descended  from  the 
original  eleven .  species,  will  now  be  fifteen  in  number. 
Owing  to  the  divergent  tendency  of  natural  selection,  the 
extreme  amount  of  difference  in  character  between  species 
au  and  zu  will  be  much  greater  than  that  between  the 
most  distinct  of  the  original  eleven  species.  The  new 
species,  moreover,  will  be  allied  to  each  other  in  a  widely 
different  manner.  Of  the  eight  descendants  from  (A)  the 
three  marked  au ,  qu,  pu,  will  be  nearly  related  from 
having  recently  branched  off  from  a 10 ;  bu  and/14,  from  hav¬ 
ing  diverged  at  an  earlier  period  from  a5,  will  be  in  some 
degree  distinct  from  the  three  first-named  species;  and 
lastly,  ou,  eu  and  mu,  will  be  nearly  related  one  to  the 
other,  but,  from  having  diverged  at  the  first  commence¬ 
ment  of  the  process  of  modification,  will  be  widely  differ¬ 
ent  from  the.  other  five  species,  and  may  constitute  a  sub¬ 
genus  or  a  distinct  genus. 

The  six  descendants  from  (I)  will  lorm  two  sub-genera 
or  genera.  But  as  the  original  species  (I)  differed  largely 
from  (A),  standing  nearly  at  the  extreme  end  of  the 
original  genus,  the  six  descendants  from  (I)  will,  owing  to 
inheritance  alone,  differ  considerably  from  the  eight  de¬ 
scendants  from  (A);  the  two  groups,  moreover,  are  sup- 


114 


RESULT  OF  TEE  ACTION 


posed  to  have  gone  on  diverging  in  different  directions. 
The  intermediate  species,  also  (and  this  is  a  very  import¬ 
ant  consideration),  which  connected  the  original  species 
(A)  and  (I),  have  all  become,  except  (F),  extinct,  and 
have  left  no  descendants.  Hence  the  six  new  species  de¬ 
scended  from  (I),  and  the  eight  descendants  fiom  (A), 
will  have  to  be  ranked  as  very  distinct  genera,  01  even  as 
distinct  sub-families. 

Thus  it  is,  as  I  believe,  that  two  or  more  genera  are 
produced  by  descent  with  modification,  from  two  or  more 
species  of  the  same  genus.  And  the  two  or  more  parent- 
species  are  supposed  to  be  descended  from  some  one  species 
of  an  earlier  genus.  In  our  diagram  this  is  indicated  by  the 
broken  lines  beneath  the  capital  letters,  converging  m  sub¬ 
branches  downward  toward  a  single  point;  this  point  rep- 
resents  a  species,  the  supposed  progenitor  of  oui  seveial 
new  sub-genera  and  genera. 

It  is  worth  while  to  reflect  for  a  moment  on  the  charac¬ 
ter  of  the  new  species  F14,  which  is  supposed  not  to  have 
diverged  much  in  character,  but  to  have  retained  the  torm 
of  (F)  either  unaltered  or  altered  only  in  a  slight  degree. 
In  this  case  its  affinities  to  the  other  fourteen  new;  species 
will  be  of  a  curious  and  circuitous  nature.  Being  de¬ 
scended  from  a  form  that  stood  between .  the  parent- 
species  (A)  and  (I),  now  supposed  to  be  extinct  and  un¬ 
known,  it  will  be  in  some  degree  intermediate  m  character 
between  the  two  groups  descended  from  these  two  species. 
But  as  these  two  groups  have  gone  on  diverging  in  charac¬ 
ter  from  the  type  of  their  parents,  the  new  species  (f  ) 
will  not  be  directly  intermediate  between  them,  but  rather: 
between  types  of  the  two  groups;  and  every  naturalist 
will  be  able  to  call  such  cases  before  his  mind.  . 

In  the  diagram  each  horizontal  line  has.  hitherto  been 
supposed  to  represent  a  thousand  generations.,  but  each 
mav  represent  a  million  or  more  generations;  it  may  also 
represent  a  section  of  the  successive  strata  of  the  earth  s 
crust  including  extinct  remains.  We  shall,  when  we  come 
to  our  chapter  on  geology,  have  to  refer  again  to  this  sub- 
iect,  and  I  think  we  shall  then  see  that  the  diagram  throws 
lio-ht  on  the  affinities  of  extinct  beings,  which,  though 
generally  belonging  to  the  same  orders,  families  or  genera, 
W'ith  those  now  living,  yet  are  often,  in  some  degree,  intei- 


OF  NATURAL  SELECTION.  n~ 

mediate  in  character  between  existing  erorms*  anri  mn 
understand  this  fact,  for  the  extinc 

dirergedTe^sJ18  ^  the  branehinS  of  descend 

nollxpWdTo  thefn1^  r  ®  PfCe8S  °f  mod>fication,  as 
now  explained,  to  the  formation  of  genera  alone  If  in 

diagram,  we  suppose  the  amount  of  change  represented 
by  each  successive  group  of  diverging  dotted  lines  to  be 
great,  the  forms  marked  «»  to  pf  those  marked  V  and 
/  ,  and  those  marked  o11  to  mu,  will  form  three  verv  dis¬ 
tinct  genera.  We  shall  also  have  two  very  distinct  genera 
descended  from  (I},  differing  widely  from  tlL  descendants  o? 
i-  .  .?.se  two  &r°uPs  of  genera  will  thus  form  two  clis- 

s-ent  modifier1-  °rdei’S’  ao?ording  to  the  amount  of  diver- 
fram  And  the°twolPP0Sf  be  rePresented  in  the  dia- 
from  two  sneets  .7il  V  l*?”1,108*  or  orders>  are  descended 
nosfd  to  K  f  51  °i'lgmal  genns>  and  these  are  sup- 
Snknown  form?  fr°m  SOme  sti11  raore  ancient  aid 

We  have  seen  that  in  each  country  it  is  the  species  be 
longing  to  the  larger  genera  which  oftenest  present  varie 
ties  or  incipient  species.  This,  indeed,  might  have  been 
pected,  for,  as  natural  selection  acts  through  one  form 

existence0"??  ad,Taut??e  over  other  forms  in  the  struggle  for 
existence,  it  will  chiefly  act  on  those  which  already  have 

some  advantage;  and  the  largeness  of  any  group  shows  that 

its  species  have  inherited  from  a  common  ancestor  some 

advantage  in  common.  Hence,  the  stri?gg“fo?  the  PrT 

duction  of  new  and  modified  descendants  will  mainlv  lie 

between  the  larger  groups  which  are  all  trying  to  increase 

n  number.  One  large  group  will  slowly  conquer  anotlm? 

of' further  varStion  ^  ?U-mber’  “d  tlu,s  lesse“  its  chance 
w“ Inn  th  li  d  improvement.  Within  the  same 
mr ge  the  later  and  more  highly  Derf eofprl 

groups,  from  branching  out  and  seizing  on  many  new 

ln,  *he  ' Pollty  of  nature,  will  constantly  tend  to  sup- 
P  ant  and  destroy  the  earlier  and  less  improved  subgroups 

peaf  aLooktog6  togr??P%antd  sub-SrouPS  wil1  finaUy  disfpl 
pear,  booking  to  the  future,  we  can  predict  thnt  iha 

groups  of  organic  beings  which  are  now  large  and  trium 

phant,  and  which  are  least  broken  up,  that  is  which  W 

as  yet  suffered  least  extinction,  will,  for  a  long  period,  con? 


116 


ON  THE  DEGREE  TO  WHICH 


tinue  to  increase.  But  which  groups  will  ultimately  pre. 
vail  no  man  can  predict;  for  we  know  that  many  groups, 
formerly  most  extensively  developed,  have  now  become  ex¬ 
tinct.  Looking  still  more  remotely  to  the  future,  we  may 
predict  that,  owing  to  the  continued  and  steady  increase  of 
the  larger  groups,  a  multitude  of  smaller  groups  will  be- 
come  utterly  extinct,  and  leave  no  modified  descendants; 
and  consequently  that,  of  the  species  living  at  any  one 
period,  extremely  few  will  transmit  descendants  to  a 
remote  futurity.  I  shall  have  to  return  to  this  subject  m  the 
chapter  on  classification,  but  I  may  add  that  as,  according 
to  this  view,  extremely  few  of  the  more  ancient  species 
have  transmitted  descendants  to  the  present  day,  and,  as 
all  the  descendants  of  the  same  species  form  a  class,  we 
can  understand  how  it  is  that  there  exist  so  few  classes  in 
each  main  division  of  the  animal  and  vegetable  kingdoms. 
Although  few  of  the  most  ancient  species  have  Jett  modi¬ 
fied  descendants,  yet,  at  remote  geological  periods,  the 
earth  may  have  been  almost  as  well  peopled  with  species  ot 
many  genera,  families,  orders  and  classes,  as  at  the  present 

time. 

ON  THE  DEGREE  TO  WHICH  ORGANIZATION  TENDS  TO 

ADVANCE. 

Natural  selection  acts  exclusively  by  the  preservation  and 
accumulation  of  variations,  which  are' beneficial  under  the 
organic  and  inorganic  conditions  to  which  each  creatine  is 
1  exposed  at  all  periods  of  life.  The  ultimate  result  is  that 
\  each  creature  tends  to  become  more  and  more  improved 
in  relation  to  its  conditions.  This  improvement  inevitably 
deads  to  the  gradual  advancement  of  the  organization  ot 
the  greater  number  of  living  beings  throughout  the  won  . 
But  here  we  enter  on  a  very  intricate  subject,  for  natural¬ 
ists  have  not  defined  to  each  other’s  satisfaction  what  is 
meant  by  an  advance  in  organization.  Among  the  verte- 
brata  the  degree  of  intellect  and  an  approach  in  structure 
to  man  clearly  come  into  play.  It  might  be  thought  that 
the  amount  of  change  which  the  various  parts  and  organs 
pass  through  in  their  development  from  embryo  to 
maturity  would  suffice  as  a  standard  of  >  comparison;  but 
there  are  cases,  as  with  certain  parasitic  crustaceans,  iu 


ORGANIZATION  TENDS  TO  ADVANCE.  117 

which  several  parts  of  the  structure  become  less  perfect,  so 
that  the  mature  animal  cannot  be  called  higher  than  its 
larva.  Von  Baer  s  standard  seems  the  most  widely  appli¬ 
cable  and  the  best,  namely,  the  amount  of  differentiation  of 

1  i  u  0  .  same  or&anic  being,  in  the  adult  state,  as  I 
should  be  inclined  to  add,  and  their  specialization  for 
different  functions;  or,  as  Milne  Edwards  would  express  it, 
ne  completeness  of  the  division  of  physiological  labor. 
But  we  shall  see  how  obscure  this  subject  is  if  we  look  for 
instance,  to  fishes,,  among  which  some  naturalists  rank 
those  as  highest  which,  like  the  sharks,  approach  nearest 
to  amphibians;  while  other  naturalists  rank  the  common 
ony  or  teleostean  fishes  as  the  highest,  inasmuch  as  they 
are  most  strictly  fish-like,  and  differ  most  from  the  other 
vertebrate  classes.  We  see  still  more  plainly  the  obscurity 
0  the  subject  by  turning  to  plants,  among  which  the 
standard  of  intellect  is  of  course  quite  excluded;  and  here 
some  botanists  rank  those  plants  as  highest  which  have 
every  organ,  as  sepels,  petals,  stamens  and  pistils,  fully 
developed  m  each  flower;  whereas  other  botanists,  probably 
with  more  truth,  look  at  the  plants  which  have  their 

several  organs  much  modified  and  reduced  in  number  as 
the  highest. 

If  we  take  as  the  standard  of  high  organization,  the 
amount  of  differentiation  and  specialization  of  the  several 
organs  m  each  being  when  adult  (and  this  will  include  the 
advancement  of  the  brain  for  intellectual  purposes), 
natural  selection  clearly  leads  toward  this  standard:  for 
all  physiologists  admit  that  the  specialization  of  organs 
inasmuch  as  in  this  state  they  perform  their  functions 
better,  is  an  advantage  to  each  being;  and  hence  the 
accumulation  of  variations  tending  toward  specialization 
is  within  the  scope  of  natural  selection.  On  the  other 
hand,  we  can  see,  bearing  in  mind  that  all  organic  beings 
are  striving  to  increase  at  a  high  ratio  and  to  seize  on 
every  unoccupied  or  less  well  occupied  place  in  the 
economy  of  nature,  that  it  is  quite  possible  for  natural 
selection  gradually  to  fit  a  being  to  a  situation  in  which 
several  organs  would  be  superfluous  or  useless:  in  such 
cases  there  would  be  retrogression  in  the  scale  of  organiza¬ 
tion.  Whether  organization  on  the  whole  has  actually  ad¬ 
vanced  from  the  remotest  geological  periods  to  the  present 


11S  ON  THE  DEGREE  TO '  tUICH 

day  will  be  more  conveniently  discussed  in  our  chapter  on 

But° it  may  be  objected  that  if  all  organic  beings  thu 
tend  to  rise  in  the  scale,  bow  is  it  that  throughout  the 
world  a  multitude  of  the  lowest  forms  still  exist;  and  how 
is  it  that  in  each  great  class  some  forms  are  far  moie 
highly  developed  than  others?  Why  have  not  the  moie 
highly  developed  forms  every  where  supplanted  and  extei- 
m  mated  the  lower?  Lamarck .who  believed .man  innate 
and  inevitable  tendency  toward  perfection  m  all  organic 
beino-s  seems  to  have  felt  this  difficulty  so  strongly  that  he 
was  Ted  to  suppose  that  new  and  simple  forms  are  continu¬ 
ally  being  produced  by  spontaneous  generation.  Science 
has  not  as  yet  proved  the  truth  of  this  belief,  whatever  the 
future  may  reveal.  On  our  theory  the  continued  existence 
of  lowly  organisms  offers  no  difficulty;  for  natural  selec¬ 
tion,  or  the  survival  of  the  fittest,  does  not  necessarily  in¬ 
clude  progressive  development — it  only  takes  advantage  o 
f  such  variations  as  arise  and  are  beneficial  to  each  creature 
‘  under  its  complex  relations  of  life.  And  it  may  be  askec 
what  advantage,  as  far  as  we  can  see,  would  it  be  to  an  l 
fusorian  animalcule— to  an  intestinal  worm— or  even  to  an 
earth-worm,  to  be  highly  organized.  Ii  it  were  no  advan¬ 
tage,  these  forms  would  be  left,  by  natural  selection,  un¬ 
improved  or  but  little  improved,  and  might  remain  for  in¬ 
definite  ages  in  their  present  lowly  condition.  And  geo. - 
oo-y  tells  us  that  some  of  the  lowest  forms,  as  the  infusoria 
and  rhizopods,  have  remained  for  an  enormous  penod  m 
nearly  their  present  state.  But  to  suppose  that -most of  the 
manv  now  existing  low  forms  have  not  m  the  least  ad 
vanned  since  the  "first  dawn  of  life  would  be  extremely 
raslr  for  every  naturalist  who  has  dissected  some  of  the 
beings  now  ranked  as  very  low  in  the  scale,  must  have  been 
struck  with  their  really  wondrous  and  beautiful  organiza- 

j  • 

^Nearly  the  same  remarks  are  applicable,  if  we  look  to  the 
different  grades  of  organization  within  the  same  giea 
group;  for  instance,  in  the  vertebrata  to  the  co-existence 
of  mammals  and  fish— among  mammalia,  to  the  co-exist¬ 
ence  of  man  and  the  ormthorhynchus— among  fishes,  to 
the  co-existence  of  the  shark  and  thelancelet  (Amphioxus) 
which  latter  fish  in  the  extreme  simplicity  of  its  structure 


ORGANIZATION  TENDS  TO  ADVANCE.  X19 

approaches  the  invertebrate  classes.  But  mammals  and 
fish  hardly  come  into  competition  with  each  other;  the  ad¬ 
vancement  of  the  whole  class  of  mammals,  or  of  certain 
members  in  this  class,  to  the  highest  grade  would  not  lead 
to  their  taking  the  place  of  fishes.  Physiologists  believe 
that  the  brain. must  be  bathed  by  wa#*m  blood  to  be  highly 
active,  and  this  requires  aerial  respiration;  so  that  warm¬ 
blooded  mammals  when  inhabiting  the  water  lie  under  a 
disadvantage  in  having  to  come  continually  to  the  surface 
to  breathe.  With  fishes,  members  of  the  shark  family 
would  not  tend  to  supplant  the  lancelet;  for  the  lancelet, 
as  I  hear  from  Fritz  Muller,  has  as  sole  companion  and 
competitor  on  the  barren  sandy  shore  of  South  Brazil,  an 
anomalous  annelid.  The  three  lowest  orders  of  mam¬ 
mals,  namely,  marsupials,  edentata,  and  rodents,  co-exist 
in  South  America  in  the  same  region  with  numerous 
monkeys,  and  probably  interfere  little  with  each  other. 
Although  organization,  on  the  whole,  may  have  advanced 
and  be  still  advancing  throughout  the  world,  yet  the  scale 
will  always  present  many  degrees  of  perfection;  for  the 
high  advancement  of  certain  whole  classes,  or  of  certain 
members  of  each  class,  does  not  at  all  necessarily  lead  to 
the  extinction  of  those  groups  with  which  they  do  not  enter 
into  close  competition.  In  some  cases,  as  we*  shall  here¬ 
after  see,  lowly  organized  forms  appear  to  have  been  pre¬ 
served  to  the  present  day,  from  inhabiting  confined  or 
peculiar  stations,  where  they  have  been  subjected  to  less 
severe  competion,  and  where  their  scanty  numbers  have  re¬ 
tarded  the  chance  of  favorable  variations  arising. 

Finally,  I  believe  that  many  lowly  organized* forms  now"' 
exist  throughout  the. world,  from  various  causes.  In  some  * 
cases  variations  or  individual  differences  of  a  favorable 
nature  may  never  have  arisen  for  natural  selection  to  act 
on  and  accumulate.  In  no  case,  probably,  has  time  suf¬ 
ficed  for  the  utmost  possible  amount  of  development.  In 
some,  few  cases  there  has  been  what  we  must  call  retro¬ 
gression  or  organization.  But  the  main  cause  lies  in  the 
fact  that  under  very  simple  conditions  of  life  a  high  organi¬ 
zation  would  be  of  no  service, — possibly  would  be  of  actual 
disservice,  as  being  of  a  more  delicate  nature,  and  more 
liable  to  be  put  out  of  order  and  injured.  J 

Looking  to  the  first  dawn  of  life,  when  all  organic  beings. 


120 


COVERGENCE  OF  CHARACTER. 


as  we  may  believe,  presented  the  simplest  structure,  liow, 
it  has  been  asked,  could  the  first  step  in  the  advancement 
or  differentiation  of  parts  have  arisen?  Mr.  Herbert 
Spencer  would  probably  answer  that,  as  soon  as  simple 
unicellular  organism  came  by  growth  or  division  to  be 
compounded  of  several  cells,  or  became  attached  to  any 
supporting  surface,  his  law  “  that  homologous  units  ot 
any  order  become  differentiated  in  proportion  as  their  rela¬ 
tions  to  incident  forces  become  different  would  come 
into  action.  But  as  we  have  no  facts  to  guide  us,  specula¬ 
tion  on  the  subject  is  almost  useless.  It  is,  however,  an 
error  to  suppose  that  there  would  be  no  struggle  for  exi&  - 
ence,  and,  consequently,  no  natural  selection,  until  many 
forms  had  been  produced:  variations  m  a  single  species 
inhabiting  an  isolated  station  might,  be  beneficial,  anu 
thus  the  whole  mass  of  individuals  might  be  modified,  or 
two  distinct  forms  might  arise.  But,  as  I  remarked  toward 
the  close  of  the  introduction,  no  one  ought  to  feel  surprise 
at  much  remaining  as  yet  unexplained  on  the  origin  ot 
species,  if  we  make  due  allowance  for  our  profound  ignor¬ 
ance  on  the  mutual  relations  of  the  inhabitants  ot  the 
world  at  the  present  time,  and  still  more  so  during  pas 


ages. 


COFTVERGEFTCE  OF  CHARACTER. 


Mr.  H.  C.  Watson  thinks  that  I  have  overrated  the  im¬ 
portance  of  divergence  of  character  (in  which,  however,  he 
apparently  believes),  and  that  convergence,  as  it  may  .  be 
called,  has  likewise  played  a  part.  If  two  species  belonging 
to  two  distinct  though  allied  genera,  had  both  produced  a 
laro-e  number  of  new  and  divergent  forms,  it  is  conceivable 
that  these  might  approach  each  other  so  closely  that  they 
would  have  all  to  be  classed  under  the  same  genus;  and 
thus  the  descendants  of  two  distinct  genera  would  converge 
into  one.  But  it  would  in  most  cases  be  extremely  rash  to  at¬ 
tribute  to  convergence  a  close  and  general  similarity  of  sti  uct- 
ure  in  the  modified  descendants  of  widely  distinct  forms. 
The  shape  of  a  crystal  is  determined  solely  by  the  molecular 
forces,  and  it  is  not  surprising  that  dissimilar  substances 
should  sometimes  assume  the  same  form;  but  with  organic 
beings  we  should  bear  in  mind  that  the.  form  of  each  de- 
J  pends  on  an  infinitude  of  complex  relations,  namely  on  the 


COVERGENCE  OF  CHARACTER. 


121 


variations  which  have  arisen,  these  being  due  to  causes  far  too 
intricate  to  be  followed  out — on  the  nature  of  tlie  variations 
which  have  been  preserved  or  selected,  and  this  depends  on 
the  surrounding  physical  conditions,  and  in  a  still  higher  de- 
,  gree  on  the  surrounding  organisms  with  which  each  being  has 
;  come  into  competition — and  lastly,  on  inheritance  (in  itself  a 
fluctuating  element)  from  innumerable  progenitors,  all  of 
which  have  had  their  forms  determined  through  equally  com- 
Jplex  relations.  It  is  incredible  that  the  descendants  of  two 
organisms,  which  had  originally  differed  in  a  marked  man¬ 
ner,  should  ever  afterward  converge  so  closely  as  to  lead 
to  a  near  approach  to  identity  throughout  their  whole 
organization.  If  this  had  occurred,  we  should  meet  with 
the  same  form,  independently  of  genetic  connection,  re¬ 
curring  in  widely  separated  geological  formations;  and  the 
balance  of  evidence  is  opposed  to  any  such  an  admission. 

Mr.  Watson  has  also  objected  that  the  continued  action 
of  natural  selection,  together  with  divergence  of  character, 
would  tend  to  make  an  indefinite  number  of  specific  forms. 
As  far  as  mere  inorganic  conditions  are  concerned,  it  seems 
probable  that  a  sufficient  number  of  species  would  soon 
become  adapted  to  all  considerable  diversities  of  heat, 
moisture,  etc. ;  but  I  fully  admit  that  the  mutual  relations 
of  organic  beings  are  more  important;  and  as  the  number 
of  species  in  any  country  goes  on  increasing,  the  organic 
conditions  of  life  must  become  more  and  more  complex. 
Consequently  there  seems  at  first  no  limit  to  the  amount  of 
profitable  diversification  of  structure,  and  therefore  no 
limit  to  the  number  of  species  which  might  be  produced. 
We  do  not  know  that  even  the  most  prolific  area  is  fully 
stocked  with  specific  forms:  at  the  Cape  of  Good  Hope  and 
in  Australia,  which  support  such  an  astonishing  number  of 
species,  many  European  plants  have  become  naturalized. 
But  geology  shows  us,  that  from  an  early  part  of  the  ter¬ 
tiary  period  the  number  of  species  of  shells,  and  that  from 
the  middle  part  of  this  same  period,  the  number  of  mam¬ 
mals  has  not  greatly  or  at  all  increased.  What  then  checks 
an  indefinite  increase  in  the  number  of  species?  The 
amount  of  life  (I  do  not  mean  the  number  of  specific 
forms)  supported  on  an  area  must  have  a  limit,  depending 
so  largely  as  it  does  on  physical  conditions;  therefore,  if 
an  area  be  inhabited  by  verv  many  species,  each  or  nearly 


SUMMARY . 


122 

each  species  will  be  represented  by  few  individuals;  and 
such  species  will  be  liable  to  extermination  from  accidental 
fluctuations  in  the  nature  of  the  seasons  or  in  the  number 
of  their  enemies.  The  process  of  extermination  in  such 
cases  would  be  rapid,  whereas  the  production  of  new  species 
must  always  be  slow.  Imagine  the  extreme  case  of  as  many 
species  as  individuals  in  England,  and  the  first  severe  winter 
or  very  dry  summer  would  exterminate  thousands  on  thou¬ 
sands  of  species.  Rare  species,  and  each  species  will  become 
rare  if  the  number  of  species  in  any  country  becomes  in¬ 
definitely  increased,  will,  on  the  principle  often  explained, 
present  within  a  given  period  few  favorable  variations;  con¬ 
sequently,  the  process  of  giving  birth  to  new  specific  foims 
would  thus  be  retarded."  When  any  species  becomes  very 
rare,  close  interbreeding  will  help  to  exterminate  it;  authors 
have  thought  that  this  comes  into  play  in  accounting  foi 
the  deterioration  of  the  aurochs  in  Lithuania,  of  red  deer 
in  Scotland  and  of  bears  in  Norway,  etc.  Lastly,  and  this 
I  am  inclined  to  think  is  the  most  important  element,  a 
dominant  species,  which  has  already  beaten  many  compet¬ 
itors  in  its  own  home,  will  tend  to  spread  and  supplant 
many  others.  Alph.  de  Candolle  has  shown  that  those 
species  which  spread  widely  tend  generally  to  spread  very 
widely,  consequently  they  will  tend  to  supplant  and  exter¬ 
minate  several  species  in  several  areas,  and  thus  check  the 
inordinate  increase  of  specific  forms  throughout  the  world. 
Dr.  Hooker  has  recently  shown  that  in  the  southeast  cor¬ 
ner  of  Australia,  where,  apparently,  there  are  many  in¬ 
vaders  from  different  quarters  of  the  globe,  the  endemic 
Australian  species  have  been  greatly  reduced  in  number. 
How  much  weight  to  attribute  to  these  several  considera¬ 
tions  I  will  not  pretend  to  say;  but  conjointly  they  must 
limit  in  each  country  the  tendency  to  an  indefinite  aug¬ 
mentation  of  specific  forms. 

SUMMARY  OF  CHAPTER. 

If  under  changing  conditions  of  life  organic  beings  pre¬ 
sent  individual  differences  in  almost  every  part  of  their 
structure,  and  this  cannot  be  disputed;  if  there  be,  owing 
to  their  geometrical  rate  of  increase,  a  severe  struggle  for 
life  at  some  age,  season  or  year;  and  this  certainly  cannot 


SUMMARY. 


123 

be  disputed;  then,  considering  the  infinite  complexity  of 
the  relations  of  all  organic  beings  to  each  other  and  to  their 
conditions  of  life,  causing  an  infinite  diversity  in  structure, 
constitution  and  habits,  to  be  advantageous  to  them,  it 
would  be  a  most  extraordinary  fact  if  no  variations  had 
ever  occurred  useful  to  each  being’s  own  welfare,  in  the 
same  manner  as^nnuiX-variations  have  oonnrmT useful  to 
man.  But  if  _ variations,  useful  to  any  organic  fining  ever 
occur,  assuredly  individuals  thus  characterized  will  have 
the_best_chance  of  being  preserved  iiTthe  sti-mro-lo  for  life: 
and  from  the  strong  principle  of  inheritancS.  these  w7)j 
tend  to, .produce  offspring  similarly  characterized.  This 
prmgi&le  of  preservation 1  or  the  survival  of  the  fit- 
jgs'BA  — ixa t.LiJLiaX^^ It  leads  ftTThe  im¬ 

provement  of  each  creaturem  relation  to  its  organic  and  in¬ 
organic  conditions  of  life,;  and  consequently,  in  most  cases, 
to  what  must  be  regarded  as  an  advance  in  organization. 
Nevertheless,  low  and  simple  forms  will  long  endnrn  if  wqll 
fitted  for  their  simple  conditions  of  life. 

Natural  selection,  on  the  principle  of  qualities  being  in- 
hented  at  corresponding  ages,  can  modify  the~_egg.  seecTor 
easily  as  the  adult.  Among  many  animals  sexual 
selection  will  have  given  its  aid  to  ordinary  selection  by 
assuring  to  the  most  vigorous  and  best  adapted  males  the 
greatest  number  of  offspring.  Sexual  selection  will  also 
give  characters  useful  to  the  males  alone  in  their  struggles 
or  rivalry  with  other  males;  and  these  characters  will  be 
transmitted  to  one  se*.  or  to  both  sexes,  according  to  the 
form  of  inheritance  which  prevails. 

Whether  natural  selection  has  really  thus  acted  in 
adapting  the  various  forms  of  life  to  their  several  condi¬ 
tions  and  stations,  must  be  judged  by  the  general  tenor 
and  balance  of  evidence  given  in  the  following  chapters. 
But  we  have  already  seen  how  it  entails  extinction;  and 
how  largely  extinction  has  acted  in  the  worlds  history, 
geology  plainly  declares.  Natural  selection,  also,  leads 
to  divergence, of — character: "for  the  mnro  nro-Mm'p.  beings 
diverge  in  structure,  habits  and  constitution,  by  so  much 
the  more  can  a  large  number  be  supported  on  the  area,  of 
which  we  see  proof  by  looking  to  the  inhabitants  of  any 
small  spot,  and  to  the  productions  naturalized  in  foreign 
lands.  Therefore,  during  the  modification  of  the  descend- 


,.,4  SUMMART. 

ants  of  any  one  specif-  and  during  the  incessant  straggle  of 
aTf  artftnifts  to  increase  liTlmmbers/tKe^SLre  diversified  the 

. —-in  th«  battle  lor  hie.  thus  the  StmUl  (tTHerences  ills 
I'inonisTiinTTarieties  of the  same  species,  steadily  tend  to 
increase,  till  they  equal  the  greater  differences  between 
species  of  the  same  genus,  or  even  of  distinct  genera. 

1  Wo  have  seen  that  it  is  the  common,  the  widely  diffused 
and  widely  ranging  species,  belonging  to  the  larger  genei  a 
within  each  class,  which  vary  most;  and  these  tend  to 
transmit  to  their  modified  offspring  that  superiority  which 

now  makes  them  dominant  in  their  divert 

ural  selection,  as  has  just  been  remarked,  lgads  to  divei 

once  of  character .  andto 

improved  and  intermediate  forms  of  life.  On  these  pun 
5^rtra-5atKr5^TEe  affimties,  aSOHe  generally  well 


prnles  the  nature  ot  tne  affinities,  anc.  —  0 
defined  distinctions  between  the 
beino-s  in  each  class  throughout  the  world,  may  De 
explained.  It  is  a  truly  wonderful  fact— the  wonder  of 
which  we  are  apt  to  overlook  from  familiarity— that  all 

animals  and  all  plants  throughout  a11  time 
should  he  related^ to  each  other  in  groups,  subordinate  to 
groups,  in  the  manner  which  we  everywhere  behold- 
.  namely  varieties  of  the  same  species  most  closely  related, 
species  of  the  same  genus  less  closely  and  mgj 
forming  sections  and  sub-genera,  species  of  distinct  genera 
much  less  closely  related,  and  genera  related  in  different 
degrees  forming"  sub-families,  families,  orders,,  sub-classes 
and  Blasses  Idio  several  subordinate  groups  in  any  class 
cannot  be  ranked  in  a  single  file,  but  seen  clustered  round 
points  and  these  round  other  points,  and  so  on  m  almost 
endless  cycles.  If  species  had  been  independently  created 
no  explanation  would  have  been  possible  of  this  kind  of  class 
ification;  but  it  is  explained  through  inheritance  and  the 
complex  action  of  natural  selection,  entailing  extinction 
and  divergence  of  character,  as  we  have  seen  illustrated  m 

simile  largely  speaks  the  truth.  The  green  and  budding 
twigs  mayS represent  existing  species;  and  those  produced 
during  former  years  may  represent  fc^long. succession 


SUMMARY. 


125 


of  extinct  species.  At  each  period  of  growth  all  the  grow¬ 
ing  twigs  have  tried  to  branch  out  on  all  sides,  and  to  over¬ 
top  and  kill  the  surrounding  twigs  and  branches,  in  the 
same  manner  as  species  and  groups  of  species  have  at  all 
times  overmastered  other  species  in  the  great  battle  for  life. 
The  limbs  divided  into  great  branches,  and  these  into  lesser 
and  lesser  branches,  were  themselves  once,  when  the  tree 
'Was  young,  budding  twigs;  and  this  connection  of  the 
former  and  present  buds  by  ramifying  branches  may  well 
represent  the  classification  of  all  extinct  and  living  species 
in  groups  subordinate  to  groups.  Of  the  many  twigs 
which  flourished  when  the  tree  was  a  mere  bush,  only  two 
or  three,  now  grown  into  great  branches,  yet  survive  and 
bear  the  other  branches;  so  with  the  species  which  lived 
during  long-past  geological  periods,  very  few  have  left 
living  and  modified  descendants.  From  the  first  growth 
of  the  tree,  many  a  limb  and  branch  has  decayed  and 
diopped  off;  and  these  fallen  branches  of  various  sizes 
may  represent  those  whole  orders,  families  and  genera 
which  have  now  no  living  representatives,  and  which  are 
known  to  us  only  in  a  fossil  state.  As  we  here  and 
there  see  a  thin,  straggling  branch  springing  from  a  fork 
low  down  in  a  tree,  and  which  by  some  chance  has  been 
favored  and  is  still  alive  on  its  summit,  so  we  occasionally 
see.  an.  animal  like  the  Ornithorhynchus  or  Fepidosiren, 
which  in  some  small  degree  connects  by  its  affinities  two 
large  branches  of  life,  and  which  has  apparently  been 
saved  from  fatal  competition  by  having  inhabited  a  pro¬ 
tected  station. .  As  buds  give. llse. by  growth  to  fresh  burls. 
ail4  these,  if  jigQrous^  branch  out  and  overtop  on  all  sides 

it  has 

W  with  t ha-great  Tree  of  Life,  which  fills  with  ifa"^ 
and  broken  ^ranches  the  crust  of  the  earth,  and  covers  the 
fiSS^ce  ever-branching  and  beau tiful  ramifications. 


126 


LAWS  OF  VARIATION. 


CHAPTER  V. 


LAWS  OF  VARIATION. 


Effects  of  changed  conditions— Use  and  disuse  combined  with 
natural  selection;  organs  of  flight  and  of  vision-Acclimatisa- 
tion — Correlated  variation— Compensation  and  economy  ot 
trrowth — False  correlations — Multiple,  rudimentary  and  lowly 
organized  structures  variable — Parts  developed  in  an  unusual 
maimer  are  highly  variable:  specific  characters  more  variable 
than  generic;  secondary  sexual  characters  variable— Species  ot 
the  same  genus  vary  in  an  analogous  manner  Reveisions  to 
long-lost  characters— Summary. 


I  have  hitherto  sometimes  spoken  as  if  the  variations 
so  common  and  multiform  with  organic  beings  under  do¬ 
mestication,  and  in  a  lesser  degree  with  those  under  nature 
—were  due  to  chance.  This,  of  course  is  a  wholly  incorrect 
expression,  but  it  serves  to  acknowledge  plainly  oui  igno- 
ranee  of  the  cause  of  each  particular  variation.  home 
authors  believe  it  to  be  as  much  the  function  of  the  repro¬ 
ductive  system  to  produce  individual  differences,  01  slight 
deviations  of  structure,  as  to  make  the  child  like  its  parents. 
But  the  fact  of  variations  and  monstrosities  occurring 
much  more  frequently  under  domestication  than  under 
nature,  and  the  greater  variability  of  species  having  wide 
ranges  than  of  those  with  restricted  ranges,  lead  to  the  con¬ 
clusion  that  variability  is  generally  related  to  the  conditions 
of  life  to  which  each  species  has  been  exposed  duung  sev¬ 
eral  successive  generations.  In  the  first  chapter  I  at¬ 
tempted  to  show  that  changed  conditions  act  in  two  ways, 
directly  on  the  whole  organization  or  on  certain  parts  alone, 
and  indirectly  through  the  reproductive  system.  >  In  all  cases 
there  are  two  factors,  the  nature  of  the  organism,  which 
is  much  the  most  important  of  the  two,  and  the  nature  of 
the  conditions.  The  direct  action  of  changed  conditions 
leads  to  definite  or  indefinite  results .  In  the  latter  case  the 
organization  seems  to  become  plastic,  and  we  ha\e  much 


LAWS  OF  VARIATION. 


127 

fluctuating  variability.  In  tlie  former  case  the  nature  of 
the  organism  is  such  that  it  yields  readily,  when  subjected 
to  certain  conditions,  and  all,  or  nearly  all,  the  individuals 
become  modified  in  the  same  way. 

It  is  very  difficult  to  decide  how  far  changed  conditions, 
such  as  of  climate,  food,  etc.,  have  acted  in  a  definite 
manner.  There  is  reason  to  believe  that  in  the  course  of 
time  the  effects  have  been  greater  than  can  be  proved  by 
clear  evidence.  But  we  may  safely  conclude  that  the 
innumerable  complex  co-adaptations  of  structure,  which 
we  see  throughout  nature  between  various  organic  beings, 
.cannot  be  attributed  simply  to  such  action.  In  the  follow- 
I  ing  cases  the  conditions  seem  to  have  produced  some  slight 
definite  effect:  E.  Forbes  asserts  that  shells  at  their 
southern  limit,  and  when  living  in  shallow  water,  are  more 
brightly  colored  than  those  of  the  same  species  from 
further  north  or  from  a  greater  depth;  but  this  certainly 
does  not  always  hold  good.  Mr.  Gould  believes  that  birds 
of  the  same  species  are  more  brightly  colored  under  a  clear 
atmosphere,  than  when  living  near  the  coast  or  on  islands; 
and  Wollaston  is  convinced  that  residence  near  the  sea 
affects  the  colors  of  insects.  Moquin-Tandon  gives  a  list 
of  plants  which,  when  growing  near  the  sea-shore,  have 
their  leaves  in  some  degree  fleshy,  though  not  elsewhere 
fleshy.  These  slightly  varying  organisms  are  interesting 
in  as  far  as  they  present  characters  analogous  to  those  pos¬ 
sessed  by  the  species  which  are  confined  to  similar  condi¬ 
tions. 

When  a  variation  is  of  the  slightest  use  to  any  being,  we 
cannot  tell  how  much  to  attribute  to  the  accumulative 
action  of  natural  selection,  and  how  much  to  the  definite 
action  of  the  conditions  of  life.  Thus,  it  is  well  known 
to  furriers  that  animals  of  the  same  species  have  thicker 
and  better  fur  the  further  north  they  live;  but  who  can 
tell  how  much  of  this  difference  may  be  due  to  the  warmest 
clad  individuals  having  been  favored  and  preserved  during 
many  generations,  and  how  much  to  the  action  of  the 
severe  climate?  For  it  would  appear  that  climate  has  some 
direct  action  on  the  hair  of  our  domestic  quadrupeds. 

Instances  could  be  given  of  similar  varieties  being  pro¬ 
duced  from  the  same  species  under  external  conditions 
©f  life  as  different  as  can  well  be  conceived;  and,  on  th,8 


128 


EFFECTS  OF  USE  AND  DISUSE. 


other  hand,  of  dissimilar  varieties  being  produced  under 
apparently  the  same  external  conditions.  Again,  innumer¬ 
able  instances  are  known  to  every  naturalist,  of  species 
keeping  true,  or  not  varying  at  all,  although  living  under 
the  most  opposite  climates.  Such  considerations  as  these 
incline  me  to  lay  less  weight  on  the  direct  action  of  the 
surrounding  conditions,  than  on  a  tendency  to  vary,  due 
to  causes  of  which  we  are  quite  ignorant. 

In  one  sense  the  conditions  of  life  may  be  said,  not  only 
to  cause  variability,  either  directly  or  indirectly,  but  like¬ 
wise  to  include  natural  selection,  for  the  conditions 
determine  whether  this  or  that  variety  shall  survive.  But 
when  man  is  the  selecting  agent,  we  clearly  see  that  the 
two  elements  of  change  are  distinct;  variability  is  in  some 
manner  excited,  but  it  is  the  will  of  man  which  accumu¬ 
lates  the  variations  in  certain  direction;  and  it  is  this  latter 
agency  which  answers  to  the  survival  of  the  fittest  under 
nature. 

EFFECTS  OF  THE  INCREASED  USE  AND  DISUSE  OF  PARTS,  AS 
\  CONTROLLED  BY  NATURAL  SELECTION. 

From  the  facts  alluded  to  in  the  first  chapter,  I  think 
there  can  be  no  doubt  that  use  in  our  domestic  animals  has 
strengthened  and  enlarged  certain  parts,  and  disuse  dimin¬ 
ished0  them;  and  that  such  modifications  are  inherited. 
Under  free  nature  we  have  no  standard  of  comparison  by 
which  to  judge  of  the  effects  of  long-continued  use  or 
disuse,  for  we  know  not  the  parent-forms;  but  many 
animals  possess  structures  which  can  be  best  explained  by 
the  effects  of  disuse.  As  Professor  Owen  has  remarked, 
there  is  no  greater  anomaly  in  nature  than  a  bird  that  cannot 
fly;  yet  there  are  several  in  this  state.  The  logger-headed 
duck  of  South  America  can  only  flap  along  the  surface 
of  the  water,  and  has  its  wings  in  nearly  the  same  condition 
as  the  domestic  Aylesbury  duck;  it  is  a  remarkable  fact 
that  the  young  birds,  according  to  Mr.  Cunningham,  can 
fly,  while  the  adults  have  lost  this  power.  As  the  larger 
ground-feeding  birds  seldom  take  flight  except  to  escape 
danger,  it  is  probable  that  the  nearly  wingless  condition  of 
several  birds,  now  inhabiting  or  which  lately  inhabited 
several  oceanic  islands,  tenanted  by  no  beasts  of  prey,  has 


EFFECTS  OF  USE  AND  DISUSE. 


129 


been  caused  by  disuse.  The  ostrich  indeed  inhabits  con¬ 
tinents,  and  is  exposed  to  danger  from  which  it  cannot 
escape  by  flight,  but  it  can  defend  itself,  by  kicking  its 
enemies,  as  efficiently  as  many  quadrupeds.  We  may 
believe  that  the  progenitor  of  the  ostrich  genus  had  habits 
like  those  of  the  bustard,  and  that,  as  the  size  and  weight 
of  its  body  were  increased  during  successive  generations, 
its  legs  were  used  more  and  its  wings  less,  until  they  be¬ 
came  incapable  of  flight. 

Kirby  has  remarked  (and  I  have  observed  the  same  fact) 
that  the  anterior  tarsi,  or  feet,  of  many  male  dung-feeding 
beetles  are  often  broken  off;  he  examined  seventeen  speci¬ 
mens  in  his  own  collection,  and  not  one  had  even  a  relic 
left.  In  the  Onites  apelles  the  tarsi  are  so  habitually  lost 
that  the  insect  has  been  described  as  not  having  them.  In 
some  other  genera  they  are  present,  but  in  a  rudimentary 
condition.  In  the  Ateuchus  or  sacred  beetle  of  the  Egyp¬ 
tians,  they  are  totally  deficient.  The  evidence  that  acci¬ 
dental  mutilations  can  be  inherited  is  at  present  not  de¬ 
cisive^  but  the  remarkable  cases  observed  by  Brown-Sequard 
in  guinea-pigs,  of  the  inherited  effects  of  operations, 
should  make  us  cautious  in  denying  this  tendency.  Hence, 
it  will  perhaps  be  safest  to  look  at  the  entire  absence  of  the 
anterior  tarsi  in  Ateuchus,  and  their  rudimentary  con¬ 
dition  in  some  other  genera,  not  as  cases  of  inherited  mu¬ 
tilations,  but  as  due  to  the  effects  of  long  continued  disuse; 
for  as  many  dung-feeding  beetles  are  generally  found  with 
their  tarsi  lost,  this  must  happen  early  in  life;  therefore 
the  tarsi  cannot  be  of  much  importance  or  be  much  used 
by  these  insects. 

In  some  cases  we  might  easily  put  down  to  disuse 
modifications  of  structure  which  are  wholly,  or  mainly  due 
to  natural  selection.  Mr.  Wollaston  has  discovered  the 
remarkable  fact  that  200  beetles,  out  of  the  550  species  (but 
more  are  now  known)  inhabiting  Maderia,  are  so  far  defi¬ 
cient  in  wings  that  they  cannot  fly;  and  that,  of  the 
twenty-nine  endemic  genera,  no  less  than  twenty-three 
have  all  their  species,  in  this  condition!  Several  facts,— 
namely,  that  beetles  in  many  parts  of  the  world  are  fre¬ 
quently  blown  to  sea  and  perish;  that  the  beetles  in  Maderia, 
as  observed  by  Mr.  Wollaston,  lie  much  concealed,  until 
the  wind  lulls  and  the  sun  shines;  that  the  proportion  of 


130  EFFECTS  OF  USE  AND  DISUSE. 

wingless  beetles  is  larger  on  the  exposed  Desertas  than  in 
Maderia  itself;  and  especially  the  extraordinary  fact,  so 
strongly  insisted  on  by  Mr.  W  ollaston,  that  certain  large 
groups' of  beetles,  elsewhere  excessively  numerous,  which 
absolutely  require  the  use  of  their  wings,  are  here  almost 
entirely  absent.  These  several  considerations  make  me  be¬ 
lieve  that  the  wingless  condition  of  so  many  Maderia 
beetles  is  mainly  due  to  the  action  of  natural  selection, 
combined  probably  with  disuse.  For  during  many  succes¬ 
sive  generations  each  individual  beetle  which  new  least, 
either  from  its  wings  having  been  ever  so  little  less  per¬ 
fectly  developed  or  from  indolent  habit,  will  have  had  the 
best  chance  of  surviving  from  not  being  blown  out  to  sea; 
and,  on  the  other  hand,  those  beetles  which  most  readily 
took  to  flight  would  oftenest  have  been  blown  to  sea,  and 
thus  destroyed. 

The  insects  in  Maderia  which  are  not  ground-feeders, 
and  which,  as  certain  flower-feeding  coleopteia  and 
lepidoptera,  must  habitually  use  their  wings  to  gain  their 
subsistence,  have,  as  Mr.  Wollaston  suspects,,  tlieii  wings 
not  at  all  reduced,  but  even  enlarged.  This  is  quite  com- 
patable  with  the  action  of  natural  selection.  For  when 
a  new  insect  first  arrived  on  the  island,  the  tendency  of 
nature  1  selection  to  enlarge  or  to  reduce  the  wings,  would 
depend  on  whether  a  greater  number  of  individuals  were 
saved  by  successfully  battling  with  the  winds,  or  by  giving 
up  the  attempt  and  rarely  or  never  flying.  As  with 
mariners  shipwrecked  near  a  coast,  it  would  have  been 
better  for  the  good  swimmers  if  they  had  been  able  to  swim 
still  further,  whereas  it  would  have  been  better  for  the 
swimmers  if  they  had  not  been  able  to  swim  at  all  and  had 
stuck  to  the  wreck. 

The  eyes  of  moles  and  of  some  burrowing  rodents  are 
rudimentary  in  size,  and  in  some  cases  are  quite  co\eied 
by  skin  and  fur.  This  state  of  the  eyes  is  probably  due  to 
gradual  reduction  from  disuse,  but  aided  peibaps  by 
natural  selection.  In  South  America,  a  burrowing  rodent, 
the  tuco-tuco,  or  Otenomys,  is  even  more  subterranean  in 
its  habits  than  the  mole;  and  I  was  assured  by  a  Spaniard, 
who  had  often  caught  them,  that  they  were  frequently 
blind.  One  which  I  kept  alive  was  certainly  in  this  con¬ 
dition,  the  cause,  as  appeared  on  dissection,  having  been 


EFFECTS  OF  USE  AND  DISUSE.  131 

inflammation  of  the  nictitating1  membrane.  As  frequent 
inflammation  of  the  eyes  mast  be  injurious  to  any  animal, 
and  as  eyes  are  certainly  not  necessary  to  animals  having 
subteiianean  habits,  a  reduction  in  their  size,  with  the 
adhesion  of  the  eyelids  and  growth  of  fur  over  them, 
might  in  such  case  be  an  ad  vantage ;  and  if  so,  natural 
selection  would  aid  the  effects  of  disuse. 

It  is  well  known  that  several  animals,  belonging  to  the 
most  different  classes,  which  inhabit  the  caves  of  Carniola 
and  Kentucky,  are  blind.  In  some  of  the  crabs  the 
foot-stalk  for  the  eyes  remains,  though  the  eye  is  gone* 
th.e  stand  for  the  telescope  is  there,  though  the  telescope 
with  its  glasses  has  been  lost.  As  it  is  difficult  to  imag¬ 
ine  that  eyes,  though  useless,  could  be  in  any  way  injurious 
to  animals  living  in  darkness,  their  loss  may  be  attributed 
to  disuse.  In  one  of  the  blind  animals,  namely,  the  cave- 
rat  (Eeotoma),  two  of  which  were  captured  by  Professor 
Silliman  at  above  half  a  mile  distance  from  the  mouth  of 
the  cave,  and  therefore  not  in  the  profoundest  depths,  the 
eyes  were  lustrous  and  of  large  size;  and  these  animals,  as 
I  am  informed  by  Professor  Silliman,  after  having  been  ex¬ 
posed  foi  about  a  month  to  a  graduated  light,  acquired  a 
dim  perception  of  objects. 

It  is  difficult  to  imagine  conditions  of  life  more  similar 
than  deep  limestone  caverns  under  a  nearly  similar  climate; 
so  that,  in  accordance  with  the  old  view  of  the  blind  ani¬ 
mals  having  been  separately  created  for  the  American  and 
European  caverns,  very  close  similarity  in  their  organiza¬ 
tion  and  affinities  might  have  been  expected.  This  is  cer¬ 
tainly  not  the  case  if  we  look  at  the  two  whole  faunas;  and 
with  lespect  to  the  insects  alone,  Schiodte  has  remarked: 
“We  are  accordingly  prevented  from  considering  the  entire 
phenomenon  in  any  other  light  than  something  purely 
local,  and  the  similarity  which  is  exhibited  in  a  few  forms 
between  the  Mammoth  Cave  (in  Kentucky)  and  the  caves 
m  Carniola,  otherwise  than  as  a  very  plain  expression  of 
that  analogy  which  subsists  generally  between  the  fauna 
of  Europe  and  of  Korth  America.”  On  my  view  we  must 
suppose  that  American  animals,  having  in  most  cases  ordi- 
luny  powers  of  vision,  slowly  migrated  by  successive  gener¬ 
ations  from  the  outer  world  into  the  deeper  and  deeper  re¬ 
cesses  of  the  Kentucky  caves,  as  did  European  animals  into 


132  effects  of  use  and  disuse. 

the  caves  of  Europe.  We  have  some  evidence  of  this  gra- 
dation  of  habit;  for,  as  Schiodte  remarks:  “  We  accord- 
ino-lv  look  upon  the  subterranean  faunas  as  small  raminca- 
tions  which  have  penetrated  into  the  earth  from  the  geo¬ 
graphically  limited  faunas  of  the  adjacent  tracts,  and 
which  as  they  extended  themselves  into  darkness,  have 
been  accommodated  to  surrounding  circumstances  Ani¬ 
mals  not  far  remote  from  ordinary  forms,  prepare  the  tran¬ 
sition  from  light  to  darkness.  Next  follow  those  that  aie 
constructed  for  twilight;  and  last  of  all,  those  destined  for 
total  darkness,  and  whose  formation  is  quite  pecmiar. 
These  remarks  of  Schiodte’s,  it  should  be  undeistocr , 
apply  not  to  the  same,  but  to  distinct  species.  By  the 
tune^  that  an  animal  had  reached,  after  numberless 
venerations,  the  deepest  recesses,  disuse  will  on  tins 
fiew  have  more  or  less  perfectly  obliterated  its  eyes 
and  natural  selection  will  often  have  effected  other 
changes,  such  as  an  increase  in  the  length  of  the 
antennae  or  palpi,  as  a  compensation  for  blindness. 
Notwithstanding  such  modifications,  we  might  expect  stil 
to  see  in  the  cave-animals  of  America,  affinities  to  the  othei 
inhabitants  of  that  continent,  and  m  those  of  Europe  to 
the  inhabitants  of  the  European  continent.  And  this  is  the 
case  with  some  of  the  American  cave-animals,  as  I  heai  liom 
Professor  Dana;  and  some  of  the  European  cave-insects  are 
very  closely  allied  to  those  of  the  surrounding  country  It 
would  be  difficult  to  give  any  rational  explanation  of  the 
affinities  of  the  blind  cave-animals  to  the  other  inhabit¬ 
ants  of  the  two  continents  on  the  ordinary  view  of  their 
'independent  creation.  That  several  of  the  inhabitants  of  the 
caves  of  the  Old  and  New  Worlds  should  be  closely  related, 
we  might  expect  from  the  well-known  relationship  of  most  ol 
their  other  productions.  As  a  blind  species  of  Bathyscia 
is  found  in  abundance  on  shady  rocks  far  from  caves,  the 
loss  of  vision  in  the  cave  species  of  this  one  genus  has  piob- 
ably  had  no  relation  to  its  dark  habitation;  for  it  is  natu¬ 
ral' that  an  insect  already  deprived  of  vision  should  readily 
become  adapted  to  dark  caverns.  Another  blind  genus 
(Anophthalmus)  offers  Ins  remarkable  peculiarity,  that  the 
species,  as  Mr.  Murray  observes,  have  not  as  yet  been  found 
anywhere  except  in  caves;  yet  those  which  inhabit  the 
several  caves  of  Europe  and  America  are  distinct;  but  it  is 


A  CCLIMA  TIZ A  TION, 


133 


possible  that  the  progenitors  of  these  several  species,  while 
they  were  furnished  with  eyes,  may  formerly  have  ranged 
over  both  continents,  and  then  have  become  extinct,  ex¬ 
cepting  in  their  present  secluded  abodes.  Far  from  feeling 
surprise  that  some  of  the  cave-animals  should  be  very 

Sni0mfii°USA  ^gassiz  has  remarked  in  regard  to  the  blind 
hsh,  the  Amblyopsis,  and  as  is  the  case  with  the  blind 
Proteus  with  reference  to  the  reptiles  of  Europe,  I  am  only 
surprised  that  more  wrecks  of  ancient  life  have  not  been 
preserved,  owing  to  the  less  severe  competition  to  which 
the  scanty  inhabitants  of  these  dark  abodes  will  have  been 


ACCLIMATIZATION. 

Habit  is  hereditary  with  plants,  as  in  the  period  of 
flowering  m  the  time  of  sleep,  in  the  amount  of  rain 
requisite  for  seeds  to  germinate,  etc.,  and  this  leads  me  to 
say  a  few  words,  on  acclimatization.  As  it  is  extremely 
common  for  distinct  species  belonging  to  the  same  genus 
to  inhabit  hot  and  cold  countries,  if  it  be  true  that  all  the 
species  of  the  same  genus  are  descended  from  a  single 
parent-form,  acclimatization  must  be  readily  effected  dur¬ 
ing  a  long  course  of  descent.  It  is  notorious  that  each 
species  is  adapted  to  the  climate  of  its  own  home:  species 
from  an  arctic  or  even  from  a  temperate  region  cannot 
endure  a  tropical  climate,  or  conversely.  So  again,  many 
succulent  plants  cannot  endure  a  damp  climate.  But  the 
degree  of  adaptation  of  species  to  the  climates  under  which 
they  live  is  often  overrated.  We  may  infer  this  from  our 
.fiequent  inability  to  predict  whether  or  not  an  imported 
ant  will  endure  our  climate,  and  from  the  number  of 
plants  and  animals  brought  from  different  countries  which 
are  here .  perfectly  healthy.  We  have  reason  to  believe 
that  species  in  a  state  of  nature  are  closely  limited  in  their 
ranges  by  the  competition  of  other  organic  beings  quite  as 
much  as,  or  more  than,  by  adaptation  to  particular  climates. 
But  whether  or  not  this  adaptation  is  in  most  cases  very 
close,  we  have  evidence  with  some  few  plants,  of  their  be"- 
coming,  to  a  certain  extent,  naturally  habituated  to  differ¬ 
ent  temperatures;  that  is,  they  become  acclimatized:  thus 
the  pmes  and  rhododendrons,  raised  from  seed  collected 


ACC  LIMA  LIZA  LION. 


134 

bv  Dr  Hooker  from  the  same  species  growing  at  different 
heights  on  the  Himalayas,  were  found  to  possess  in  this 
country  different  constitutional  powers  of  resisting  co  d. 
Mr  Thwaites  informs  me  that  he  has  observed  similar 
facts  in  Ceylon;  analogous  observations  have  been  made 
by  Mr  H.  C.  Watson  on  European  species  of  plants 
brought  from  the  Azores  to  England;  and  I  could  give 
other  cases.  In  regard  to  animals,  several  authentic 
instances  could  be  adduced  of  species  haying  largely 
extended,  within  historical  times,  their  range  from  warmer 
to  colder  latitudes,  and  conversely;  but  we  do  not  posi¬ 
tively  know  that  these  animals  were  strictly  adapted  to 
their  native  climate,  though  in  all  ordinary  cases  we 
assume  such  to  be  the  case;  nor  do  we  know  that  they 
have  subsequently  become  specially  acclimated  to  their 
new  homes,  so  as  to  be  better  fitted  for  them  than  they 

were  at  first.  , 

As  we  may  infer  that  our  domestic  animals  were  origin¬ 
ally  chosen  by  uncivilized  man  because  they  were  useful, 
and  because  they  bred  readily  under  confinement,  and  not 
because  they  were  subsequently  found  capable  ot  lai- 
extended  transportation,  the  common  and  extraordinary 
capacity  in  our  domestic  animals  of  not  only  withstanding 
the  most  different  climates,  but  of  being  perfectl)  fertile 
(a  far  severer  test)  under  them,  may  be  used  as  an  argument 
that  a  large  proportion  of  other  animals  now  m  a  state  ot 
nature  could  easily  be  brought  to  bear  widely  different 
climates.  We  must  not,  however,  push  the  foregoing 
argument  too  far,  on  account  of  the  probable  origin  ox 
some  of  our  domestic  animals  from  several  wild  stocks;  the 
blood,  for  instance,  of  a  tropical  and  arctic  wolf  may  per¬ 
haps  be  mingled  in  our  domestic  breeds.  1  he  rat  and 
mouse  cannot  be  considered  as  domestic  animals,  but  they 
have  been  transported  by  man  to  many  parts  of  the  world, 
and  now  have  a  far  wider  range  than  any  other  rodent;  tor 
they  live  under  the  cold  climate  of  Faroe  in  the  north  and 
of  the  Falklands  in  the  south,  and  on  many  an  island  m 
the  torrid  zones.  Hence  adaptation  to  any  special  climate 
may  be  looked  at  as  quality  readily  grafted  on  an  innate 
wide  flexibility  of  constitution,  common  to  most  animals. 
On  this  view,  the  capacity  of  enduring  the  most  different 
climates  by  man  himself  and  by  his  domestic  animals,  and 


A  CCLIMA  TIZA  TTChV.  135 

the  fact  of  the  extinct  elephant  and  rhinoceros  having  for¬ 
merly  endured  a  glacial  climate,  whereas  the  living  species 
are  now  all  tropical  or  sub-tropical  in  their  habits,  ought 
not  to  be  looked  at  as  anomalies,  but  as  examples  of  a  very 
common  flexibility  of  constitution,  brought,  under  peculiar 
circumstances,  into  action.  r 

How  much  of  the  acclimatization  of  species  to  any 
peculiar  climate  is  due  to  mere  habit,  and  how  much  to  the 
natural  selection  of  varieties  having  different  innate  con¬ 
stitutions,  and  how  much  to  both  means  combined,  is  an 
obscure  question.  That  habit  or  custom  has  some  influ¬ 
ence,  I  must  believe,  both  from  analogy  and  from  the  in¬ 
cessant  advice  given  in  agricultural  works,  even  in  the 
ancient  Encyclopedias  of  China,  to  be  very  cautious  in 
transporting  animals  from  one  district  to  another.  And 
as  it  is  not  likely  that  man  should  have  succeeded  in  select- 
mg  so  many  breeds  and  sub-breeds  with  constitutions 
specially  fitted  for  their  own  districts,  the  result  must,  I 
think,  be  due  to  habit.  On  the  other  hand,  natural  selec- 
iou  would  inevitably  tend  to  preserve  those  individuals 
which  were  born  with  constitutions  best  adapted  to  any 
country  which  they  inhabited.  In  treatises  on  many  kinds 
ot  cultivated  plants,  certain  varieties  are  said  to  with¬ 
stand  certain  climates  better  than  others;  this  is  strik- 
lngly  shown  in  works  on  fruit-trees  published  in  the  United 
states,  m  which  certain  varieties  are  habitually  recom¬ 
mended  for  the  northern  and  others  for  the  southern  states: 
and  as  most  of  these  varieties  are  of  recent  origin,  they  can 
not  owe  thrnr  constitutional  differences  to  habit.  The  case 
o  he  Jerusalem  artichoke,  which  is  never  propagated  in 
ngland  by  seed,  and  of  which,  consequently,  new  varieties 
lave  not  been  produced,  has  even  been  advanced,  as  prov¬ 
ing  that  acclimatization  cannot  be  effected,  for  it  is  now  as 
tender  as  ever  it  was!  The  case,  also,  of  the  kidney-bean 
Has  been  often  cited  for  a  similar  purpose,  and  with  much 
greater  weight;  but  until  some  one  will  sow,  during  a  score 
ox  generations,  his  kidney-beans  so  (early  that  a  very  large 
proportion  are  destroyed  by  frost,  and  then  collect  seed 
irom  the  few  survivors,  with  care  to  prevent  accidental 
crosses,  and  then  again  get  seed  from  these  seedlings,  with 
the  same  precautions,  the  experiment  cannot  be  said  to 
have  been  tried.  Nor  let  it  be  supposed  that  differences  in 


136 


CORRELATED  VARIATION. 


the  constitution  of  seedling  kidney-beans  never  appear,  for 
an  account  has  been  published  how  much  more  hardy  some 
seedlings  are  than  others;  and  of  this  fact  I  have  myself 
observed  striking  instances. 

On  the  whole,  we  may  conclude  that  habit,  or  use  and 
disuse,  have,  in  some  cases,  played  a  considerable  part  in 
the  modification  of  the  constitution  and  structure;  but 
that  the  effects  have  often  been  largely  combined  with,  and 
sometimes  overmastered  by,  the  natural  selection  of  innate 
variations. 


CORRELATED  VARIATION. 

I  mean  by  this  expression  that  the  whole  organization  is 
so  tied  together,  during  its  growth  and  development,  that 
when  slight  variations  in  any  one  part  occur  and  are  accu¬ 
mulated  through  natural  selection,  other  parts  become 
modified.  This  is  a  very  important  subject,  most 
imperfectly  understood,  and  no  doubt  wholly  different 
classes  of  facts  may  be  here  easily  confounded  together. 
We  shall  presently  see  that  simple  ‘  inheritance  often  gives 
the  false  appearance  of  correlation.  One  of  the  most 
obvious  real  cases  is.  that  variations  of  structure  arising  in 
the  young  or  larvae  naturally  tend  to  affect  the  structure  of 
the  mature  animal.  The  several  parts  which  are  homo¬ 
logous,  and  which,  at  an  early  embryonic  period,  are 
identical  in  structure,  and  which  are  necessarily  exposed  to 
similar  conditions,  seem  eminently  liable  to  vary  in  a  like 
manner:  we  see  this  in  the  right  and  left  sides  of  the 
body  varying  in  the  same  manner;  in  the  front  and  hind 
legs,  and  even  in  the  jaws  and  limbs,  varying  together, 
for  the  lower  jaw  is  believed  by  some  anatomists  to  be 
homologous  with  the  limbs.  These  tendencies,  I  do  not 
doubt,  may  be  mastered  more  or  less  completely  by  natural 
selection;  thus  a  family  of  stags  once  existed  with  an 
antler  only  on  one  side;  and  if  this  had  been  of  any  great 
use  to  the  breed,  it  might  probably  have  been  rendered  per¬ 
manent  by  selection. 

Homologous  parts,  as  has  been  remarked  by  some  authors, 
tend  to  cohere;  this  is  often  seen  in  monstrous  plants: 
and  nothing  is  more  common  than  the  union  of  homolo¬ 
gous  parts  in  normal  structures,  as  in  the  union  of  the 


CORRELATED  VARIATION, 


13? 


petals  into  a  tube.  Hard  parts  seem  to  affect  the  form  of 
adjommg  soft  parts;  it  is  believed  by  some  authors  that 
with  birds  the  diversity  in  the  shape  of  the  pelvis  causes 
the  remarkable  diversity  in  the  shape  of  their  kidneys. 
Otheis  believe  that  the  shape  of  the  pelvis  in  the  human 
nl{ °™er  lnlluences  by  pressure  the  shape  of  the  head  of  the 
child.  In  snakes,  according  to  Schlegel,  the  form  of  the 
body  and  the  manner  of  swallowing  determine  the  position 
anm/orm,°^  several  of  the  most  important  viscera. 

Ihe  nature  of  the  bond  is  frequently  quite  obscure.  M.  Is ,t 
Geoff roy  St.  Hilaire  has  forcibly  remarked  that  certain  mal- 
cqnformations  frequently,  and  that  others  rarely,  coexist 
without  our  being  able  to  assign  any  reason.  What  can 
be  more  singular  than  the  relation  in  cats  between  com¬ 
plete  whiteness  and  blue  eyes  with  deafness,  or  between 
the  tortoise-shell  color  and  the  female  sex;  or  in 
pigeons,  between  their  feathered  feet  and  skin  betwixt  the 
outer  toes,  or  between  the  presence  of  more  or  less  down  on 
the  young  pigeon  when  first  hatched,  with  the  future  color 
Jr  1 T  or  again,  the  relation  between  the  hair  and 

the  teeth  m  the  naked  Turkish  dog,  though  here  no  doubt 
homology  comes  into  play?  With  respect  to  this  latter 
case  of  correlation,  I  think  it  can  hardly  be  accidental  that 
the.  two  orders  of  mammals  which  are  most  abnormal  in 
their  dermal  covering,  viz.,  cetacea  (whales)  and  edentata 
(aimadilloes,  scaly  ant-eaters,  etc.),  are  likewise  on  the 
whole  the  most  abnormal  in  their  teeth,  but  there  are  so 
many  exceptions  to  this  rule,  as  Mr.  Mivart  has  remarked, 
that  it  has  little  value. 


know  of  no  case  better  adapted  to  show  the  importance 
ot  the  laws  of  correlation  and  variation,  independently  of 
utility,  and  therefore  of  natural  selection,  than  that  of  the 
aitterence  between  the  outer  and  inner  flowers  in  some 
compositous  and  umbelliferous  plants.  Everyone  is 
familiar  with  the  difference  between  the  ray  and  central 
florets  of,  for  instance,  the  daisy,  and  this  difference  is 
often  accompanied  with  the  partial  or  complete  abortion  of 
the  reproductive  organs.  But  in  some  of  these  plants  the 
seeds  also  differ  in  shape  and  sculpture.  These  differences 
have  sometimes  been  attributed  to  the  pressure  of  the  in- 
volucra  on  the  florets,  or  to  their  mutual  pressure,  and  the 
shape  of  the  seeds  m  the  ray  florets  of  some  composite 


138 


CORRELATED  VARIATION. 


countenances  this  idea;  but  with  the  umbelliferse  it  is  by 
no  means,  as  Dr.  Hooker  informs  me,  the  species  with  the 
densest  heads  which  most  frequently  differ  m  their  inner 
and  outer  flowers.  It  might  have  been  thought  that  the 
development  of  the  ray-petals,  by  drawing  nourishment 
from  the  reproductive  organs  causes  their  aboition,  but 
this  can  hardly  be  the  sole  cause,  for  m  some  composite 
the  seeds  of  the  outer  and  inner  florets  differ,  without  any 
difference  in  the  corolla.  Possibly  these  seveial  differ¬ 
ences  may  be  connected  with  the  different  flow  of  nutn- 
ment  toward  the  central  and  external  flowers.  We  know, 
at  least,  that  with  irregular  flowers  those  nearest  to  the 
axis  are  most  subject  to  peloria,  that  is  to  become  abnormally 
symmetrical.  I  may  add,  as  an  instance  of  this  fact,  and 
as  a  striking  case  of  correlation,  that  in  many  pelargoniums 
the  two  upper  petals  in  the  central  flower  of  the  truss  often 
lose  their  patches  of  darker  color;  and  when  this  occurs, 
the  adherent  nectary  is  quite  aborted,  the  central  flower 
thus  becoming  peloric  or  regular.  When  the  color  is 
absent  from  only  one  of  the  two  upper  petals,  the  nectary 
is  not  quite  aborted  but  is  much  shortened. 

With  respect  to  the  development  of  the  corolla,  bpren- 
gel’s  idea  that  the  ray-florets  serve  to  attract  insects,  whose 
agency  is  highly  advantageous,  or  necessary  for  the  fertili¬ 
zation  of  these  plants,  is  highly  probable;  and  if  so,  nat- 
ural  selection  may  have  come  into  play.  But  with  respect 
to  the  seeds,  it  seems  impossible  that  their  differences  m 
shape,  which  are  not  always  correlated  with  any  difference 
in  the  corolla,  can  be  in  any  way  beneficial;  yet  m  the  um¬ 
belliferse  these  differences  are  of  such  apparent  importance 

_ _ the  seeds  being  sometimes  orthospermous  in  the  exterior 

flowers  and  ccelospermous  in  the  central  flowers — that  the 
elder  De  Candolle  founded  his  main  divisions  in  the  order 
on  such  characters.  Hence  modifications  of  structure, 
viewed  by  systematists  as  of  high  value,  may  he  who  y 
due  to  the  laws  of  variation  and  correlation,  without 
being,  as  far  as  we  can  judge,  of  the  slightest  service  to  the 

S^Ve  may  often  falsely  attribute  to  correlated  variation 
structures  which  are  common  to  whole  groups  of  species, 
and  which  in  truth  are  simply  due  to  inheritance;  for  an 
ancient  progenitor  may  have  acquired  through  natuiai 


COMPENSA TION  AND  ECONOMY  OF  GROWTH.  139 

selection  some  one  modification  in  structure,  and,  after 
thousands  of  generations,  some  other  and  independent 
modification;  and  these  two  modifications,  having  been 
transmitted  to  a  whole  group  of  descendants  with  diverse 
habits,  would  naturally  be  thought  to  be  in  some  necessary 
manner  correlated.  Some  other  correlations  are  apparently 
due  to  the  manner  in  which  natural  selection  can  alone 
act.  For  instance,  Alph.  de  Candolle  has  remarked  that 
winged  seeds  are  never  found  in  fruits  which  do  not  open- 
1  should  explain  this  rule  by  the  impossibility  of  seeds 
gradually  becoming  winged  through  natural  selection, 
unless  the  capsules  were  open;  for  in  this  case  alone  could 
the  seeds,  which  were  a  little  better  adapted  to  be  wafted 

by  the  wind,  gain  an  advantage  over  others  less  well  fitted 
lor  wide  dispersal. 

COMPENSATION-  AND  ECONOMY  OF  GROWTH. 

The  elder  Gfeoffroy  and  Goethe  propounded,  at  about  the 
same  time,  their  law  of  compensation  or  balancement  of 
growth;  or,  as  Goethe  expressed  it,  “in  order  to  spend  on 
one  side,  nature  is  forced  to  economize  on  the  other  side.” 
1  think  this  holds  true  to  a  certain  extent  with  our  domes¬ 
tic  productions:  if  nourishment  flows  to  one  part  or  organ 
m  excess,  it  rarely  flows,  at  least  in  excess,  to  another  part: 
lius  it  is  difficult  to  get  a  cow  to  give  much  milk  and  to 
fatten  readily.  The  same  varieties  of  the  cabbage  do  not 
yieid  abundant  and  nutritious  foliage  and  a  copious  supply 
of  oil-bearing  seeds.  #  When  the  seeds  in  our  fruits  become 
atrophied,  the  fruit  itself  gains  largely  in  size  and  quality. 
In  our  poultry,  a  large  tuft  of  feathers  on  the  head  is  gen- ✓ 
erally  accompanied  by  a  diminished  comb,  and  a  large 
beard  by  diminished  wattles.  With  species  in  a  state  of 
nature  it  can  hardly  be  maintained  that  the  law  is  of  uni- 
vmsal  application;  but  many  good  observers,  more  espe¬ 
cially  botanists,  believe  in  its  truth.  I  will  not,  however 
here  give  any  instances,  for  I  see  hardly  any  way  of  distin¬ 
guishing  between  the  effects,  on  the  one  hand,  of  a  part 
Ging  largely  developed  through  natural  selection  and 
another  and  adjoining  part  being  reduced  by  the  same  pro¬ 
cess  or  oy  disuse,  and,  on  the  other  hand,  the  actual  with¬ 
drawal  of  nutriment  from  one  part  owing  to  the  excess  of 
growth  in.  another  and  adjoining  part. 


1 40  MUL TIPLE  AND  R  UDIMENTAR  T 

I  suspect,  also,  that  some  of  the  cases  of  compensation 
which  have  been  advanced,  and  likewise  some  other  facts, 
may  be  merged  under  a  more  general  principle,  namely, 
that  natural  selection  is  continually  trying  to  econo¬ 
mize  every  part  of  the  organization.  If  under  changed 
conditions  of  life  a  structure,  before  useful,  becomes  less 
useful,  its  diminution  will  be  favored,  for  it  will  profit  the 
individual  not  to  have  its  nutriment  wasted  m  building  up 
a  useless  structure.  I  can  thus  only  understand  a  fact  with 
which  I  was  much  struck  when  examining  cirnpedes,  and 
of  which  many  analogous  instances  could  be  given:  namely, 
that  when  a  cirripede  is  parasitic  within  another  cirnpede 
and  is  thus  protected,  it  loses  more  or  less  completely  its 
own  shell  or  carapace.  This  is  the  case  with  the  ma.e 
Ibla,  and  in  a  truly  extraordinary  manner  with  the  1  roteo- 
lepas:  for  the  carapace  in  all  other  cirnpedes  consists  ot 
the  three  highly  important  anterior  segments  of  the  head 
enormously  developed,  and  furnished  with  great  nerves 
and  muscles;  but  in  the  parasitic  and  protected  Jrioteole- 
pas,  the  whole  anterior  part  of  the  head  is  reduced  to  the 
merest  rudiment  attached  to  the  bases  of  the  piehensilo 
antennae.  Now  the  saving  of  a  large  and  complex  struc¬ 
ture,  when  rendered  superfluous,  would  be  a  decided  ad¬ 
vantage  to  each  successive  individual  of  the  species;  for  m 
the  struggle  for  life  to  which  every  animal  is  exposed,  each 
would  have  a  better  chance  of  supporting  itself,  by  less 

nutriment  being  wasted.  ,  .  ,,  , 

Thus,  as  I  believe,  natural  selection  will  tend  m  the  long 
run  to  reduce  any  part  of  the  organization,  as  soon  as  it 
becomes,  through  changed  habits,  superfluous,  without  by 
any  means  causing  some  other  part  to  be  largely  devel¬ 
oped  in  a  corresponding  degree.  And  conversely,  that 
natural  selection  may  perfectly  well  succeed  in  laigely  de¬ 
veloping  an  organ  without  requiring  as  a  necessary  com¬ 
pensation  the  reduction  of  some  adjoining  part. 

MULTIPLE,  RUDIMENTARY,  AND  LOWLY-ORGANIZED  STRUC¬ 
TURES  ARE  VARIABLE. 

It  seems  to  be  a  rule,  as  remarked  by  Is.  Geoffroy  Sfc. 
Hilaire,  both  with  varieties  and  species,  that  when  any  part 
or  organ  is  repeated  many  times  in  the  same  individual  (as 


STRUCTURES  VARIABLE.  141 

the  vertebrae  in  snakes,  and  the  stamens  in  polyandrous 
flowers)  the  number  is  variable;  whereas  the  same  part  or 
organ,  when  it  occurs  in  lesser  numbers,  is  constant.  The 
same  author,  as  well  as  some  botanists,  have  further  re¬ 
marked  that  multiple  parts  are  extremely  liable  to  vary 
in  structure.  As  ‘‘vegetable  repetition,"  to  use  Professor 
.  en  s  expression,  is  a  sign  of  low  organization,  the  fore- 
gomg  statements  accord  with  the  common  opinion  of  natu¬ 
ralists,  that  beings  which  stand  low  in  the  scale  of  nature 
are  more  variable  than  those  which  are  higher.  I  presume 
that  lowness  here  means  that  the  several  parts  of  the 
oiganization  have  been  but  little  specialized  for  particular 
functions;  and  as  long  as  the  same  part  has  to  perform 
diversified  work,  we  can  perhaps  see  why  it  should  remain 
variable,  that  is,  why  natural  selection  should  not  have 
preserved  or  rejected  each  little  deviation  of  form  so  care- 
uny  as  when  the  part  has  to  serve  for  some  one  special 
purpose.  In  the  same  way  that  a  knife  which  has  to  cut 
all  sorts  of  things  may  be  of  almost  any  shape;  while  a  tool 
for  some  particular  purpose  must  be  of  some  particular 
shape.  .Natural  selection,  it  should  never  be  forgotten 
can  act  solely  through  and  for  the  advantage  of  each  being* 
Rudimentary  parts,  as  is  generally  admitted,  are  apt  to 
be  highly  vanable.  We  shall  have  to  recur  to  this  subject* 
and  I  will  here  only  add  that  their  variability  seems  to  re¬ 
sult  from  their  uselessness,  and  consequently  from  natural 

selection  having  had  no  power  to  check  deviations  in  their 
structure. 

A  PART  DEVELOPED  IN  ANY  SPECIES  IN  AN  EXTRAORDI¬ 
NARY  DEGREE  OR  MANNER,  IN  COMPARISON  WITH  THE 
SAME  PART  IN  ALLIED  SPECIES,  TENDS  TO  BE  HIGHLY 
VARIABLE. 


Several  years  ago  I  was  much  struck  by  a  remark  to  the 
above  effect  made  by  Mr.  Waterhouse.  Professor  Owen, 
also,  seems  to  have  come  to  a  nearly  similar  conclusion! 
It  is  hopeless  to  attempt  to  convince  any  one  of  the  truth 
of  the  above  proposition  without  giving  the  long  array  of 
facts  which  I  have  collected,  and  which  cannot  possibly  bo 

I  n  "1  .  ,  I  can  only  state  my  conviction  that  it  is 
a  lute  of  high  generality.  I  am  aware  of  several  causes  of 


143  UNUSUALLY  DEVELOPED  PARTS 

error,  but  I  hope  that  I  have  made  due  allowances  fot 
them.  It  should  be  understood  that  the  rule  by  no  means 
applies  to  any  part,  however  unusually  developed,  unless 
it  be  unusually  developed  in  one  species  or  m  a  few  species 
in  comparison  with  the  same  part  in  many  closely  allied 
species/  Thus,  the  wing  of  the  bat  is  a  most  abnormal 
structure  in  the  class  of  mammals,  but  the  rule  would  not 
apply  here,  because  the  whole  group  of  bats  possesses 
wings;  it  would  apply  only  if  some  one  species  had  wings 
developed  in  a  remarkable  manner  m  comparison  with  the 
other  species  of  the  same  genus.  The  rule  applies  very 
strongly  in  the  case  of  secondary  sexual  characters,  when 
displayed  in  any  unusual  manner.  The  term,  secondary 
sexual*  characters,  used  by  Hunter,  relates  to  characters 
which  are  attached  to  one  sex,  but  are  not  directly  con¬ 
nected  with  the  act  of  reproduction.  The  rule  applies  to 
males  and  females;  but  more  rarely  to  the  females,  as  they 
seldom  offer  remarkable  secondary  sexual  characters.  1  ie 
rule  being  so  plainly  applicable  in  the  case  of  secondary 
sexual  characters,  may  be  due  to  the  great  variability  of 
these  characters,  whether  or  not  displayed  m  any  unusual 
manner— of  which  fact  I  think  there  can  be  little  doubt. 
But  that  our  rule  is  not  confined  to  secondary  sexual  char¬ 
acters  is  clearly  shown  in  the  case  of  hermaphrodite  cirn- 
pedes;  I  particularly  attended  to  Mr.  Waterhouse  s  remark, 
while  investigating  this  order,  and  I  am  fully  convinced 
that  the  rule  almost  always  holds  good.  1  shall,  m  a 
future  work,  give  a  list  of  all  the  more  remarkable  cases. 

I  will  here  give  only  one,  as  it  illustrates  the  rule  in  its 
largest  application.  The  opercular  valves  of  sessile  cirn- 
pedes  (rock  barnacles)  are,  in  every  sense  of  the  word,  very 
important  structures,  and  they  differ  extremely  little  even 
in  distinct  genera;  but  in  the  several  species  of  one  genus, 
Pyrgoma,  these  valves  present  a  marvellous  amount  ot 
diversification;  the  homologous  valves,  in  the  different 
species  being  sometimes  wholly  unlike  m  shape;  and  the 
amount  of  variation  in  the  individuals  of  the  same  species 
is  so  great  that  it  is  no  exaggeration  to  state  tnat  the 
varieties  of  the  same  species  differ  more  from  each  other  in 
the  characters  derived  from  these  important  organs,  than 
do  the  species  belonging  to  other  distinct  genera. 

As  with  birds  the  individuals  of  the  same  species,  m- 


HIGHLY  VARIABLE. 


143 


habiting  the  same  country,  vary  extremely  little,  I  have 
particularly  attended  to  them;  and  the  rule  certainly  seems 
to  hold  good  m  this  class.  I  cannot  make  out  that  it 
applies  to> plants,  and  this  would  have  seriously  shaken  mv 
belief  m  its  truth  had  not  the  great  variability  in  plants 
made  it  particularly  difficult  to  compare  their  relative  de¬ 
grees  of  variability. 

When  we  see  any  part  or  organ  developed  in  a  remark¬ 
able  degree  or  manner  in  a  species,  the  fair  presumption  is 
that  it  is  of  high  importance  to  that  species:  nevertheless 

1S,  ,In,  ,th,IS  case  eminently  liable  to  variation.  Why 
should  this  be  so?  On  the  view  that  each  species  has  been 
independently  created,  with  all  its  parts  as  we  now  see 
them,  1  can  see  no  explanation.  But  on  the  view  that 
groups  of  species  are  descended  from  some  other  species 
and  have  been  modified  through  natural  selection,  I  think 
we  can  obtain  some  light.  First  let  me  make  some  pre¬ 
liminary  remarks.  If,  in  our  domestic  animals,  any  part 
°'te  "I110’6  an™al  be  neglected,  and  no  selection  be  ap¬ 
plied,  that  part  (for  instance,  the  comb  in  the  Dorking 
fowl)  or  the  whole  breed  will  cease  to  have  a  uniform 
character:  and  the  breed  may  be  said  to  be  degenerating. 
In  rudimentary  organs,  and  in  those  which  have  been  but 
little  specialized  for  any  particular  purpose,  and  perhaps 
m  polymorphic  groups,  we  see  a  nearly  parallel  case;  for  in 
such  cases  natural  selection  either  has  not  or  cannot  have 
come  into  full  play,  and  thus  the  organization  is  left  in  a 
fluctuating  condition.  But  what  here  more  particularly 
concerns  us  is,  that  those  points  in  our  domestic  animals, 
which  at  the  present  time  are  undergoing  rapid  change  bv 
continued  selection  are  also  eminently  liable  to  variation. 
.Look  at  the  individuals  of  the  same  breed  of  the  pigeon 
and  see  what  a  prodigious  amount  of  difference  there  is  in 
the  beaks  of  tumblers,  in  the  beaks  and  wattle  of  carriers 
in  the  carriage  and  tail  of  fantails,  etc.,  these  being  the 
points  now  mainly  attended  to  by  English  fanciers.  Even 
in  the  same  sub-breed,  as  in  that  of  the  short-faced  tumbler 
,  1S  notoriously  difficult  to  breed  nearly  perfect  birds,  many 
departing  widely  from  the  standard.  There  may  truly  be 
said  to  be  a  constant  struggle  going  on  between,  on  the 
one  hand,  the  tendency  to  reversion  to  a  less  perfect  state, 
as  well  as  an  innate  tendency  to  new  variations,  and,  on 


144  UNUSUALLY  DEVELOPED  PARTS 

the  other  hand,  the  power  of  steady  selection  to  keep  L  2 
breed  true.  In  the  long  run  selection  gains  the  day, 
and  we  do  not  expect  to  fail  so  completely  as  to  breed  a 
bird  as  coarse  as  a  common  tumbler  pigeon  from  a  good 
short-faced  strain.  But  as  long  as  selection  is  lapidly 
going  on,  much  variabilit}7  in  the  parts  undergoing  modi¬ 
fication  may  always  be  expected. 

Now  let  us  turn  to  nature.  When  a  part  has  been 
developed  in  an  extraordinary  manner  in  any  one  species, 
compared  with  the  other  species  of  the  same  genus,  we 
may  conclude  that  this  part  has  undergone  an  extraordinary 
amount  of  modification  since  the  period  when  the  several 
species  branched  off  from  the  common  progenitor  of  the 
o’enus.  This  period  will  seldom  be  remote  in  any  extreme 
degree,  as  species  rarely  endure  for  more  than  one  geolog¬ 
ical  period.  An  extraordinary  amount,  of  modification 
implies  an  unusually  large  and  long-continued  amount  of 
variability,  which  has  continually  been  accumulated  by 
natural  selection  for  the  benefit  of  the  species.  But  as  the 
variability  of  the  extraordinarily  developed  part  or  organ 
has  been  so  great  and  long-continued,  within  a  period 
not  excessively  remote,  we  might,  as  a  general  rule,  still 
expect  to  find  more  variability  in  such  paits  than  in 
other  parts  of  the  organization  which  have  remained  for 
a  much  longer  period  nearly  constant.  And  this,  I  am 
convinced,  is  the  case.  That  the  struggle  between  nat¬ 
ural  selection  on  the  one  hand,  and  the  tendency  to  1  ever¬ 
sion  and  variability  on  the  other  hand,  will  in  the  course 
of  time  cease 5  and  that  the  most  abnormally  developed 
organs  may  be  made  constant,  I  see  no  reason  to  doubt. 
Hence,  when  an  organ,  however  abnormal  it  may  be,  has 
been  transmitted  in  approximately  the  same  condition  to 
many  modified  descendants,  as  in  the  case  of  the  wing  of 
the  bat,  it  must  have  existed,  according  to  our  theory,  for 
an  immense  period  in  nearly  the  same  state \  and  thus  it 
has  come  not  to  be  more  variable  than  any  other  structure. 
It  is  only  in  those  cases  in  which  the  modification  has  been 
comparatively  recent  and  extraordinarily  great  that  we 
ouo-ht  to  find  the  generative  variability,  as  it  may  be 
called,  still  present  in  a  high  degree.  For  in  this  case  the 
variability  will  seldom  as  yet  have  been  fixed  by  the  con¬ 
tinued  selection  of  the  individuals  varying  in  the  required 


HIGHLY  VARIABLE. 


145 


manner  and  degree,  and  by  tlie  continued  rejection  of  those 
tending  to  revert  to  a  former  and  less  modified  condition. 

SPECIFIC  CHARACTERS  MORE  VARIABLE  THAN  GENERIC 

CHARACTERS. 

The  principle  discussed  under  the  last  heading  may  be 
applied  to  our  present  subject.  It  is  notorious  that  spe¬ 
cific  characters  are  more  variable  than  generic.  To  ex¬ 
plain  by  a  simple  example  what  is  meant:  if  in  a  large 
genus  of  plants  some  species  had  blue  flowers  and  some 
had  red,  the  color  would  be  only  a  specific  character,  and 
no  one  would  be  surprised  at  one  of  the  blue  species  vary¬ 
ing  into  red,  or  conversely;  but  if  all  the  species  had  blue 
flowers,  the  color  would  become  a  generic  character,  and 
its  variation  would  be  a  more  unusual  circumstance.  I 
have  chosen  this  example  because  the  explanation  which 
most  naturalists  would  advance  is  not  here  applicable, 
namely,  that  specific  characters  are  more  variable  than  gen¬ 
eric,  because  they  are  taken  from  parts  of  less  physiological 
importance  than  those  commonly  used  for  classing  genera. 

I  believe  this  explanation  is  partly,  yet  only  indirectly, 
true;  I  shall,  however,  have  to  return  to  this  point  in  the 
chapter  on  Classification.  It  would  be  almost  superfluous 
to  adduce  evidence  in  support  of  the  statement,  that  ordi-  * 
nary  specific  characters  are  more  variable  than  generic; 
but  with  respect  to  important  characters,  I  have  repeatedly 
noticed  in  works  on  natural  history,  that  when  an  author 
remarks  with  surprise  that  some  important  organ  or  part, 
which  is  generally  very  constant  throughout  a  large  group 
of  species,  differs  considerably  in  closely  allied  species,  it  is 
often  variable  in  the  individuals  of  the  same  species.  And 
this  fact  shows  that  a  character,  which  is  generally  of  gen¬ 
eric  value,  when  it  sinks  in  value  and  becomes  only  of  spe¬ 
cific  value,  often  becomes  variable,  though  its  physiological 
importance  may  remain  the  same.  Something  of  the  same 
kind  applies  to  monstrosities:  at  least  Is.  Geoffrov  St. 
Hilaire  apparently  entertains  no  doubt,  that  the  more  an 
organ  normally  differs  in  the  different  species  of  the  same 
group,  the  more  subject  it  is  to  anomalies  in  the  individ¬ 
uals. 

On  the  ordinary  view  of  each  species  having  been  inde- 


146  SECONDARY  SEXUAL  CHARACTERS  VARIABLE. 

pendently  created,  why  should  that  part  of  the  struc¬ 
ture,  which  differs  from  the  same  part  in  other 
independently  created  species  of  the  same  genus,  be  more 
variable  than  those  parts  which  are  closely  alike  in  the 
several  species?  I  do  not  see  that  any  explanation  can  be 
given.  But  on  the  view  that  species  are  only  strongly 
marked  and  fixed  varieties,  we  might  expect  often  to  find 
them  still  continuing  to  vary  in  those  parts  of  their  struc¬ 
ture  which  have  varied  within  a  moderately  recent  period, 
and  which  have  thus  come  to  differ.  Or  to  state  the  case 
in  another  manner:  the  points  in  which  all  the  species  of  a 
genus  resemble  each  other,  and  in  which  they  differ  from 
allied  genera,  are  called  generic  characters;  and  these  char¬ 
acters  may  be  attributed  to  inheritance  from  a  common 
progenitor,  for  it  can  rarely  have  happened  that  natural  selec¬ 
tion  will  have  modified  several  distinct  species,  fitted  to 
more  or  less  widely  different  habits,  in  exactly  the  same 
manner:  and  as  those  so-called  generic  characters  have  been 
inherited  from  before  the  period  when  the  several  species 
first  branched  off  from  their  common  progenitor,  and  sub¬ 
sequently  have  not  varied  or  come  to  differ  in  any  degree, 
or  only  in  a  slight  degree,  it  is  not  probable  that  they 
should  vary  at  the  present  day.  On  the  other  hand,  the 
points  in  which  species  differ  from  other  species  of  the 
same  genus  are  called  specific  characters;  and  as  these 
specific  characters  have  varied  and  come  to  differ  since  the 
period  when  the  species  branched  off  from  a  common 
progenitor,  it  is  probable  that  they  should  still  often  be  in 
some  degree  variable — at  least  more  variable  than  those 
parts  of  the  organization  which  have  for  a  very  long  period 
remained  constant. 

SECONDARY  SEXUAL  CHARACTERS  VARIABLE. 

1  think  it  will  be  admitted  by  naturalists,  without  my 
entering  on  details,  that  secondary  sexual  characters  are 
highly  variable.  It  will  also  be  admitted  that  species  of 
the  same  group  differ  from  each  other  more  widely  in  their 
secondary  sexual  characters,  than  in  other  parts  of  their 
organization:  compare,  for  instance,  the  amount  of  differ¬ 
ence  between  the  males  of  gallinaceous  birds,  in  which 
secondary  sexual  characters  are  strongly  displayed,  with 


SECONDARY  SEXUAL  CHARACTERS  VARIABLE.  U7 

nflhZZ  °f  dif?er®°ce  between  the  females.  The  cause 
.  ,  gmal  variability  of  these  cliaracters  is  not  mani 
fest;  but  we  can  see  why  they  should  not  have  been  Z- 
i  end  as  constant  and  uniform  as  others,  for  they  are  ac 
cumulated  by  sexual  selection,  which  is  less  X  Z  Z 
action  than  ordinary  selection,  as  it  does  not  entail  death 

WwZ  girS  fe'Vel'  ofeP ri“g  to  ««  less  favored  males’ 
Whatever  the  cause  may  be  of  the  variability  of  secondary 

tfon  willhhTveehadaSa *h?J  *"*  higZ  variabfe>  sexual  selec- 
non  will  Have  had  a  wide  scope  for  action,  and  mav  thus 

have  succeeded  m  giving  to  the  species  of  ihe  sameCr 
respect?1,  am°Unt  of  dlfierence  in  these  than  in  otlJr 

.  b  ’3  a  remarkable  fact,  that  the  secondary  differences 
between  the  two  sexes  of  the  same  species  are  ZZX 
displayed  m  the  very  same  parts  of  the  organization  in 
Of  “hiB  ftTf188-?/  tl;e  Sa-me : Vns  differ  fro, teach  othe 

Of  .his  fact  I  will  give  in  illustration  the  two  first  in 

fZnZhnlVZt s ?°  StaUf  ?n.my  list;  and  as  the  dif- 

relation  can  hardly  be  accidental VheT^1  natnr^  th2 

S  b"‘,  “  ,lle  Ei|sw»- *>  "'«i- 

nomber  liK^ "tt  tl7 “ 

species.  Again  in  the  fossorial  hymenoptera  the  neura° 

because  com  motto  la  °llaracter  of,the  highest  importance, 
the  two  sexes  of  the  same  SDeoio^  Qjv.  t  r  i  i  i  i 

anterior  antenna  and  by  the  fifth  pa“  of  legs  “the  snL  fic 

ffiSt'",  principally  given  by  these  orfan^ 

the  BDMfe?  of tfJ  meanln«  on  vie«':  I  look  at  all 
V,  I  f  V!  ot  the  same  genus  as  having  as  certainly 

of  mivded  fr°m  ac0mm°n  progenitor,  as  have  the  two  sexes 

structare  o/PtehTS-co  Cons«<l«®Btly, .whatever  part  of  the 

nThZ'l'v8’  TZ  ?ria“e>  var.!timi0sr’of0this°pahSwoeuait 

it  highly  probable,  be  taken  advantage  of  by  natural  and 


148  distinct  species  present 

sexual  selection,  in  order  to  fit  the  several  places  in  the 
economy  of  nature,  and  likewise  to  fit  the  two  sexes  of  the 
same  species  to  each  other,  or  to  fit  the  males  to  strugg  e 
with  other  males  for  the  possession  of  the  females. 

Finally,  then,  I  conclude  that  the  greater  variability  of 
specific  characters,  or  those  which  distinguish  species  from 
species  than  of  generic  characters,  or  those  which  aie  pos¬ 
sessed  by  all  the  species;  that  the  frequent  extreme  yana- 
bility  of  any  part  which  is  developed  in  a  species  in  an 
extraordinary  manner  in  comparison  with  the  same  part  in 
its  congeners;  and  the  slight  degree  of  vai  lability  < 
part,  however  extraordinarily  it  may  be  developed,  if  it  be 
common  to  a  whole  group  of  species;  that  the  great  vai  la¬ 
bility  of  secondary  sexual  characters  and  then  gicat  dint 
ence  in  closely  allied  species;  that  secondary  sexual  and 
ordinary  specific  differences  are  generally  displayed  in  the 
same  parts  of  the  organization,  are  all  principles  closely 
connected  together.  All  being  mainly  due  to  the  species 
of  the  same  group  being  the  descendants  of  a  common 
progenitor,  from  whom  they  have  inherited  much  in 
common,  to  parts  which  have  recently  and  largely  varied 
being  more  likely  still  to  go  on  varying  than  parts  whicn 
have  long  been  inherited  and  have  not  varied,  to  natmal 
selection  having  more  or  less  completely,  according  to  tie 
lapse  of  time,  overmastered  the  tendency  to  reversion  and 
to  further  variability,  to  sexual  selection  being  less  ngi 
than  ordinary  selection,  and  to  variations  m  the  same 
parts  having  been  accumulated  by  natural  and  sexual 
selection,  and  having  been  thus  adapted  for  secondaiy 
sexual,  and  for  ordinary  purposes. 

DISTINCT  SPECIES  PRESENT  ANALOGOUS  VARIATIONS,  SO 

THAT  A  VARIETY  OF  ONE  SPECIES  OFTEN  ASSUMES  A 

CHARACTER  PROPER  TO  AN  ALLIED  SPECIES,  OR  RE¬ 
VERTS  TO  SOME  OF  THE  CHARACTERS  OF  AN  EARLY 

PROGENITOR. 

These  propositions  will  be  most  readily  understood  by 
looking;  to  our  domestic  races.  The  most  distinct  breeds 
of  the  pigeon,  in  countries  widely  apart,  present  sub-varie¬ 
ties  with  reversed  feathers  on  the  head,  and  with  feathers 


ANALOGOUS  VARIATIONS. 


149 


on  the  feet,  characters  not  possessed  by  the  aboriginal 
rock-pigeon;  these  then  are  analogous  variations  in  two  or 
more  distinct  races.  The  frequent  presence  of  fourteen  or 
even  sixteen  tail-feathers  in  the  pouter  may  be  con¬ 
sidered  as  a  variation  representing  the  normal  structure  of 
another  race,  the  fantail.  I  presume  that  no  one  will 
doubt  that  all  such  analogous  variations  are  due  to  the 
several  races  of  the  pigeon  having  inherited  from  a  common 
parent  the  same  constitution  and  tendency  to  variation,, 
when  acted  on  by  similar  unknown  influences.  In  the 
vegetable  kingdom  we  have  a  case  of  analogous  variation, 
in  the  enlarged  stems,  or  as  commonly  called  roots,  of  the 
Swedish  turnip  and  ruta-baga,  plants  which  several  bot¬ 
anists  rank  as  varieties  produced  by  cultivation  from  a 
common  parent:  if  this  be  not  so,  the  case  will  then  be  one 
of  analogous  variation  in  two  so-called  distinct  species;  and 
to  these  a  third  may  be  added,  namely,  the  common  turnip. 
According  to  the  ordinary  view  of  each  species  having  been 
independently  created,  we  should  have  to  attribute  this 
similarity  in  the  enlarged  stems  of  these  three  plants,  not 
to  the  vera  causa  of  community  of  descent,  and  a  conse¬ 
quent  tendency  to  vary  in  a  like  manner,  but  to  three 
separate  yet  closely  related  acts  of  creation.  Many  similar 
cases  of  analogous  variation  have  been  observed  by  Naudir 
in  the  great  gourd  family,  and  by  various  authors  in  or  J 
cereals.  Similar  cases  occurring  with  insects  under  ns 
ural  conditions  have  lately  been  discussed  with  much  abii 
ity  by  Mr.  Walsh,  who  has  grouped  them  under  his  law  of 
equable  variability. 

With  pigeons,  however,  we  have  another  case,  namely, 
the  occasional  appearance  in  all  the  breeds,  of  slaty-blue 
birds  with  two  black  bars  on  the  wings,  white  loins,  a  bar 
at  the  end  of  the  tail,  with  the  outer  feathers  externallv 
edged  near  their  basis  with  white.  As  all  these  marks  are 
characteristic  of  the  parent  rock-pigeon,  I  presume  that  no 
one  will  doubt  that  this  isX'a  case  of  reversion,  and  not  of  a 
new  yet  analogous  variation  appearing  in  the  several 
breeds.  We  may,  I  think,  confidently  come  to  this  con¬ 
clusion,  because,  as  we  have  seen,  these  colored  marks  are 
eminently  liable  to  appear  in  the  crossed  offspring  of  two 
distinct  and  differently  colored  breeds;  and  in  this  case 
there  is  nothing  in  the  external  conditions  of  life  to  cause 


150 


DISTINCT  SPECIES  PRESENT 


the  reappearance  of  the  slaty-bine,  with  the  several  marks, 
beyond  the  influence  of  the  mere  act  of  crossing  on  the 

laws  of  inheritance.  ......  , 

No  doubt  it  is  a  very  surprising  fact  that  characters 

should  reappear  after  having  been  lost  for  many,  probably 
for  hundreds  of  generations.  But  when  a  breed  has  been 
crossed  only  once  by  some  other  breed,  the  offspring  occa¬ 
sionally  show  for  many  generations  a  tendency  to  revert  m 
character  to  the  foreign  breed— some  say,  for  a  dozen  or  ev en 
a  score  of  generations.  After  twelve  generations,  the  pro¬ 
portion  of  blood,  to  use  a  common  expression,  from  one 
ancestor,  is  only  one  in  2048;  and  yet,  as  we. see ,  it  is  gen¬ 
erally  believed  that  a  tendency  to  reversion  is  retained  by 
this  remnant  of  foreign  blood.  In  a  breed  which  has  not 
been  crossed,  but  in  which  both  parents  have  lost  some 
character  which  their  progenitor  possessed,  the  tendency, 
whether  strong  or  weak,  to  reproduce  the  lost  character 
might,  as  was  formerly  remarked,  for  all  that  we  can  see  to 
the3  contrarv,  be  transmitted  for  almost  any  number  of  gen¬ 
erations.  When  a  character  which  has  been  lost  m  a  breed^ 
reappears  after  a  great  number  of  generations,  the  most 
probable  hypothesis  is,  not  that  one  individual  suddenly 
takes  after  an  ancestor  removed  by  some  hundred  genera¬ 
tions,  but  that  in  each  successive  generation  the  character 
in  question  has  been  lying  latent,  and  at  last,  under 
unknown  favorable  conditions,  is  developed.  With  the 
barb-pigeon,  for  instance,  which  very  rarely  produces  a 
blue  bird,  it  is  probable  that  there  is  a  latent  tendency  in 
each  generation  to  produce  blue  plumage.  The  abstract 
improbability  of  such  a  tendency  being  transmitted  through 
a  vast  number  of  generations,  is  not  greater,  than  that  ot 
quite  useless  or  rudimentary  organs  being  similarly  trans¬ 
mitted.  A  mere  tendency  to  produce  a  rudiment  is  indeed 

sometimes  thus  inherited.  , 

As  all  the  species  of  the  same  genus,  are. supposed  to  be 
descended  from  a  common  progenitor,  it  might  beexpecte  ^ 
that  they  would  occasionally  vary  in  an  analogous  manner; 
so  that  the  varieties  of  two  or  more  species  would  resemble 
each  other,  or  that  a  variety  of  one  species  would  resemble 
in  certain  characters  another  and  distinct  species,  this 
other  species  being,  according  to  our  view,  only  a  ^el- 
marked  and  permanent  variety.  But  characters  exclusively 


ANALOGOUS  VARIATIONS.  151 

due  to  analogous  variation  would  probably  be  of  an  unim¬ 
portant  nature,  for  the  preservation  of  all  functionally  im¬ 
portant  characters  will  have  been  determined  through 
natural  selection,  m  accordance  with  the  different  habits 
of  the  species.  It  might  further  be  expected  that  the 
species  of  the  same  genus  would  occasionally  exhibit  rever¬ 
sions  to  long-lost  characters.  As,  however,  we  do  not 
know  the  common  ancestor  of  any  natural  group,  we 
cannot  distinguish  between  reversionary  and  analogous 
characters.  If,  for  instance,  we  did  not  know  that  the 
parent  rock-pigeon  was  not  feather-footed  or  turn-crowned 
we  could  not  have  told,  whether  such  characters  in  our 
domestic  breeds  were  reversions  or  only  analogous  varia¬ 
tions;  but  we  might  have  inferred  that  the  blue  color  was 
a  case  of  reversion  from  the  number  of  the  markings 
which  are  correlated  with  this  tint,  and  which  would  not 
probaby  have  all  appeared  together  from  simple  variation. 
More  especially  we  might  have  inferred  this  from  the  blue 
color  and  the  several  marks  so  often  appearing  when  dif¬ 
ferently  colored  breeds  are  crossed.  Hence,  although  under 
nature  it  must  generally  be  left  doubtful,  what  lases  are 
reversions  to  formerly  existing  characters,  and  what  are 
new  but  analogous  variations,  yet  we  ought,  on  our  theory, 
sometimes  to  find  the  varying  offspring  of  a  species  assum 
ing  characters  which  are  already  present  in  other  members 
of  the  same  group.  And  this  undoubtedly  is  the  case. 

he  difficulty  in  distinguishing  variable  species  is  largely 
due  to  the  varieties  mocking,  as  it  were,  other  species  of 
the  same  genus.  A  considerable  catalogue,  also,  could  be 
given  of  forms  intermediate  between  two  other  forms 
which  themselves  can  only  doubtfully  be  ranked  as  species’; 
and  this  shows,  unless  all  these  closely  allied  forms  be  con¬ 
sidered  as  independently  created  species,  that  they  have  in 
varing  assumed  some  of  the  characters  of  the  others.  But 
tlie  best  evidence  of  analogous  variations  is  afforded  by 
parts  or  organs  which  are  generally  constant  in  character 
but  which  occasionally  vary  so  as  to  resemble,  in  some 
degree,  the  same  part  or  organ  in  an  allied  species.  I  have 
collected  a  long  list  of  such  cases;  but  here,  as  before,  I  lie 
under  the  great  disadvantage  of  not  being  able  to  give 
wiem.  I  can  only  repeat  that  such  cases  certainly  occur, 
ana  seem  to  me  very  remarkable. 


152 


DISTINCT  SPECIES  PRESENT 


I  will  however,  give  one  curious  and  complex  case,  not 
indeed  as  affecting  any  important  character,  but  from 
occurring  in  several  species  of  the  same  genus,  partly 
under  domestication  and  partly  under  nature.  It  is  a  case 
almost  certainly  of  reversion.  The  ass  sometimes i  has 
very  distinct  tranverse  bars  on  its  legs,  like  those  on 
the^ leas  of  the  zebra.  It  has  been  asserted  that  these  are 
plainest  in  the  foal,  and,  from  inquiries  which  I  have 
bade  I  believe  this  to  be  true.  The  stripe  on  the  shoulder  is 
sometimes  double,  and  is  very  variable  m  length  and  outline 
A  white  ass,  but  not  an  albino,  has  been  descubed  without 
either  spinal  or  shoulder  stripe;  and  these  stripes  are  some¬ 
times  very  obscure,  or  actually  quite  lost,  m  dark-colored 
•isses  The  koulan  of  Pallas  is  said  to  have  been  seen  with  a 
double  shoulder-stripe.  Mr.  Blyth  has  seen  a  specimen 
of  the  hemionus  with  a  distinct  shouldei -stupe,  » 

it  properly  has  none;  and  I  have  been  informed  by  Colonel 
Poole  that  the  foals  of  this  species  are  generally  striped  oil  the 
legs  and  faintly  on  the  shoulder.  The  quagga,  though  so 
plainly  barred  like  a  zebra  over  the  body,  is  without  ba.s 
on  the  legs;  but  Dr.  Gray  has  figured  one  specimen  with 
very  distinct  zebra-like  bars  on  the  hocks. 

With  respect  to  the  horse,  I  have  collected  cases  m 
England  of  the  spinal  stripe  in  horses  of  the  most  distinct 
breeds  and  of  all  colors;  transverse  bars  om  the  legs  are  not 
rare  in  duns,  mouse  duns,  and  in  one  instance  in  a  chest¬ 
nut;  a  faint  shoulder-stripe  may  sometimes  be  seen  m 
duns,  and  I  have  seen  a  trace  in  a  bay  hoi se.  My  -on 
made  a  careful  examination  and  sketch  for  me  of  a  dun 
Belgian  cart-horse  with  a  double  stripe  on  each  shoulder 
and  with  leg-stripes.  I  have  myself  seen  a  dun  Devon¬ 
shire  pony,  and  a  small  dun  Welsh  pony  has  been  carefully 
described  to  me,  both  with  three  parallel  stripes  on  each 

In  the  northwest  part  of  India  the  Kattywar  breed  of 
horses  is  so  generally  striped,  that,  as  I  hear  from  Colon® 
Poole,  who  examined  this  breed  for  the  Indian  Govern¬ 
ment,  a  horse  without  stripes  is  not  considered  as  purely 
bred.  The  spine  is  always  striped,  the  legs  are  generally 
barred,  and  the  shoulder-stripe,  which  is  sometimes  double 
and  sometimes  treble,  is  common;  the  side  of  the  face 
moreover,  is  sometimes  sb-lned.  The  stripes  are  often 


ANALOGOUS  VARIATIONS. 


153 


plainest  in  the  foal,  and  sometimes  quite  disappear  in  old 
horses.  Colonel  Poole  has  seen  both  gray  and  bay  Katty- 
war  horses  striped  when  first  foaled.  I  have  also  reason  to 
suspect,  from  information  given  me  by  Mr.  W.  W.  Ed¬ 
wards,  that  with  the  English  race-horse  the  spinal  stripe  is 
much  commoner  in  the  foal  than  in  the  full-grown  animal. 
I  have  myself  recently  bred  a  foal  from  a  bay  mare  (off¬ 
spring  of  a  Turkoman  horse  and  a  Flemish  mare)  by  a  bay 
English  race-horse.  This  foal,  when  a  week  old,  was 
marked  on  its  hinder  quarters  and  on  its  forehead  with 
numerous  very  narrow,  dark,  zebra-like  bars,  and  its  legs 
were  feebly  striped.  All  the  stripes  soon  disappeared  com¬ 
pletely.  Without  here  entering  on  further  details  I  may 
state  that  I  have  collected  cases  of  leg  and  shoulder-stripes 
in  horses  of  very  different  breeds  in  various  countries  from 
Britain  to  Eastern  China,  and  from  Norway  in  the  north 
to  the  Malay  Archipelago  in  the  south.  In  all  parts  of  the 
world  these  stripes  occur  far  oftenest  in  duns  and  mouse- 
duns.  By  the  term  dun  a  large  range  of  color  is  included, 
from  one  between  brown  and  black  to  a  close  approach  to 
cream  color. 

I  am  aware  that  Colonel  Hamilton  Smith,  who  has  writ¬ 
ten  on  this  subject,  believes  that  the  several  breeds  of  the 
horse  are  descended  from  several  aboriginal  species,  one  of 
which,  the  dun,  was  striped;  and  that  the  above-described 
appearances  are  all  due  to  ancient  crosses  with  the  dun 
stock.  But  this  view  may  be  safely  rejected,  for  it  is 
highly  improbable  that  the  heavy  Belgian  cart-horse, 
Welsh  ponies,  Norwegian  cobs,  the  lanky  Kattywar  race, 
etc.,  inhabiting  the  most  distant  parts  of  the  world, 
should  all  have  been  crossed  with  one  supposed  aboriginal 
stock. 

Now  let  us  turn  to  the  effects  of  crossing  the  several 
species  of  the  horse  genus.  Kollin  asserts  that  the  com¬ 
mon  mule  from  the  ass  and  horse  is  particularly  apt  to 
have  bars  on  its  legs;  according  to  Mr.  Gosse,  in  certain 
parts  of  the  United  States,  about  nine  out  of  ten  mules 
have  striped  legs.  I  once  saw  a  mule  with  its  legs  so  much 
striped  that  any  one  might  have  thought  that  it  was  a 
hybrid  zebra;  and  Mr.  W.  0.  Martin,  in  his  excellent 
treatise  on  the  horse,  has  given  a  figure  of  a  similar  mule. 
In  four  colored  drawings,  which  I  have  seen,  of  hybrids 


154 


DISTINCT  SPECIES  PRESENT 


between  the  ass  and  zebra,  the  legs  were  much  more  plainly 
barred  than  the  rest  of  the  body;  and  in  one  of  them  there 
was  a  double  shoulder-stripe.  In  Lord  Morton’s  famous 
hybrid,  from  a  chestnut  mare  and  male  quagga,  the  hybrid 
and  even  the  pure  offspring  subsequently  produced  from 
the  same  mare  by  a  black  Arabian  sire,  were  much  more 
plainly  barred  across  the  legs  than  is  even  the  pure  quagga. 
Lastly,  and  this  is  another  most  remarkable  case,  a  hybrid 
has  been  figured  by  Dr.  Gray  (and  he  informs  me  that  he 
knows  of  a  second  case)  from  the  ass  and  the  hemionus; 
and  this  hybrid,  though  the  ass  only  occasionally  has  stripes 
on  his  legs  and  the  hemionus  has  none  and  has  not  even  a 
shoulder- stripe,  nevertheless  had  all  four  legs  barred,  and 
had  three  short  shoulder-stripes,  like  those  on  the  dun 
Devonshire  and  Welsh  ponies,  and  even  had  some  zebra- 
like  stripes  on  the  sides  of  its  face.  W ith  respect  to  this 
last  fact,  I  was  so  convinced  that  not  even  a  stripe  of  color 
appears  from  what  is  commonly  called  chance,  that  I  was 
led  solely  from  the  occurrence  of  the  face-stripes  on  this 
hybrid  from  the  ass  and  hemionus  to  ask  Colonel  Poole 
whether  such  face-stripes  ever  occurred  in  the  eminently 
striped  Kattywar  breed  of  horses,  and  was,  as  we  have 
seen,  answered  in  the  affirmative. 

What  now  are  we  to  say  to  these  several  facts?  We  see 
several  distinct  species  of  the  horse  genus  becoming,  by 
simple  variation,  striped  on  the  legs  like  a  zebra,  or  striped 
on  the  shoulders  like  an  ass.  In  the  horse  we  see  this 
tendency  strong  whenever  a  dun  tint  appears — a  tint  which 
approaches  to  that  of  the  general  coloring  of  the  other 
species  of  the  genus.  The  appearance  of  the  stripes  is  not 
accompanied  by  any  change  of  form,  or  by  any  other  new 
character.  We  see  this  tendency  to  become  striped  most 
strongly  displayed  in  hybrids  from  between  several  of  the 
most  distinct  species.  Now  observe  the  case  of  the  several 
breeds  of  pigeons:  they  are  descended  from  a  pigeon  (in¬ 
cluding  two  or  three  sub-species  or  geographical  races)  of 
a  bluish  color,  with  certain  bars  and  other  marks;  and 
when  any  breed  assumes  by  simple  variation  a  bluish  tint, 
these  bars  and  other  marks  invariably  reappear;  but  with¬ 
out  any  other  change  of  form  or  character.  When  the 
oldest  and  truest  breed  of  various  colors  are  crossed,  we  see 
a  strong  tendency  for  the  blue  tint  and  bars  and  marks 


ANALOGOUS  VARIATIONS. 


155 

to  reappear  in  the  mongrels.  I  have  stated  that  the 
most  probable  hypothesis  to  account  for  the  reappear¬ 
ance  of  very  ancient  characters,  is  — that  there  is  a 
tendency  in  the  young  of  each  successive  generation 
to  produce  the  long-lost  character,  and  that  this  ten¬ 
dency,  from  unknown  causes,  sometimes  prevails.  And 
we  have  just  seen  that  in  several  species  of  the  horse 
genus  the  stripes  are  either  plainer  or  appear  more  com¬ 
monly  in  the  young  than  in  the  old.  Call  the  breeds  of 
pigeons,  some  of  which  have  bred  true  for  centuries, 
species;  and  how  exactly  parallel  is  the  case  with  that  of 
the  species  of  the  horse  genus!  For  myself,  I  venture  con¬ 
fidently  to  look  back  thousands  on  thousands  of  genera¬ 
tions,  and  I  see  an  animal  striped  like  a  zebra,  but  perhaps 
otherwise  very  differently  constructed,  the  common  parent 
of  our  domestic  horse  (whether  or  not  it  be  descended 
from  one  or  more  wild  stocks)  of  the  ass,  the  hemionus, 
quagga  and  zebra. 

He  who  believes  that  each  equine  species  was  independ¬ 
ently  created,  will,  I  presume,  assert  that  each  species  has 
been  created  with  a  tendency  to  vary,  both  under  nature 
and  under  domestication,  in  this  particular  manner,  so  as 
often  to  become  striped  like  the  other  species  of  the  genus; 
and  that  each  has  been  created  with  a  strong  tendency, 
when  crossed  with  species  inhabiting  distant  quarters  of 
the  world,  to  produce  hybrids  resembling  in  their  stripes, 
not  their  own  parents,  but  other  species  of  the  genus.  To 
admit  this  view  is,  as  it  seems  to  me,  to  reject  a  real  for  an 
unreal,  or  at  least  for  an  unknown  cause.  It  makes  the 
works  of  God  a  mere  mockery  and  deception;  I  would 
almost  as  soon  believe  with  the  old  and  ignorant  cosmo- 
gonists,  that  fossil  shells  had  never  lived,  but  had  been 
created  in  stone  so  as  to  mock  the  shells  living  on  the  sea¬ 
shore. 


SUMMARY. 

Our  ignorance  of  the  laws  of  variation  is  profound. 
Not  in  one  case  out  of  a  hundred  can  we  pretend  to  assign 
any  reason  why  this  or  that  part  has  varied.  But  when¬ 
ever  we  have  the  means  of  instituting  a  comparison,  the 
same  laws  appear  to  have  acted  in  producing  the  lesser  dif- 


156 


SUMMARY. 


ferences  between  varieties  of  the  same  species,  and  the 
greater  diffences  between  species  of  the  same  genus.  Changed 
conditions  generally  induce  mere  fluctuating  variability, 
but  sometimes  they  cause  direct  and  definite  effects,  and 
these  may  become  strongly  marked  in  the  course  of  tune, 
though  we  have  not  sufficient  evidence  on  this  head. 
Habit  in  producing  constitutional  peculiarities,  and  use  m 
strengthening,  and  disuse  in  weakening  and  diminishing 
organs,  appear  in  many  cases  to  have  been  potent  m  their 
effects.  Homologous  parts  tend  to  vary  m  the  same  man¬ 
ner,  and  homologous  parts  tend  to  cohere.  Modifications 
in  hard  parts  and  in  external  parts  sometimes  affect  softei 
and  internal  parts.  When  one  part  is  largely  developed,  per¬ 
haps  it  tends  to  draw  nourishment  from  the  adjoining  paits, 
and  every  part  of  the  structure  which  can  be  saved  without 
detriment  will  be  saved.  Changes  of  structure  at  an  early 
age  may  affect  parts  subsequently  developed;  and  mam 
cases  of  correlated  variation,  the  nature  of  which  we  are 
unable  to  understand,  undoubtedly  occur.  Mutiple  parts 
are  variable  in  number  and  in  structure,  perhaps  arising 
from  such  parts  not  having  been  closely  specialized  for  any 
particular  function,  so  that  their  modifications  ha\  e  not  been 
closely  checked  by  natural  selection.  .  It  follows  probably 
from  this  same  cause,  that  organic  beings  low  m  the  scale 
are  more  variable  than  those  standing  higher  m  the  scale, 
and  which  have  their  whole  organization  more  specialized. 
Rudimentary  organs,  from  being  useless,  are  not  regulated  by 
natural  selection,  and  hence  ,'je  variable.  Specific  characters 
—that  is,  the  characters  which  have  come  to  differ  since 
the  several  species  of  the  same  genus  branched  off  from 
a  common  parent— are  more  variable  than  generic  char¬ 
acters.  or  those  which  have  long  been  inherited,  and  have 
not  differed  within  this  same  period.  In  these  remarks  we 
have  referred  to  special  parts  or  organs  being  still  vari¬ 
able,  because  they  have  recently  varied  and  thus  come  to 

differ;  but  we  have  also  seen  in  the  second  chapter  that  the 
same  principle  applies  to  the  whole  individual;  for  in  a 
district  where  many  species  of  a  genus  are 
that  is,  where  there  has  been  much  former  vanation  ana 
differentiation,  or  where  the  manufactory  of  new  specific 
forms  has  been  actively  at  work— in  that  district  and 
among  these  species,  we  now  find,  on  an  average,  most 


SUMMARY. 


15? 


varieties.  Secondary  sexual  characters  are  highly  variable, 
and  such  characters  differ  much  in  the  species  of  the  same 
group.  Variability  in  the  same  parts  of  the  organization 
has  generally  been  taken  advantage  of  in  giving  secondary 
sexual  differences  to  the  two  sexes  of  the  same  species,  and 
specific  differences  to  the  several  species  of  the  same  genus. 
Any  part  or  organ  developed  to  an  extraordinary  size  or  in 
an  extraordinary  manner,  in  comparison  with  the  same 
part  or  organ  in  the  allied  species,  must  have  gone  through 
an  extraordinary  amount  of  modification  since  the  genus 
arose;  and  thus  we  can  understand  why  it  should  often 
still  be  variable  in  a  much  higher  degree  than  other  parts; 
for  variation  is  a  long-continued  and  slow  process,  and 
natural  selection  will  in  such  cases  not  as  yet  have  had 
time  to  overcome  the  tendency  to  further  variability  and 
to  reversion  to  a  less  modified  state.  But  when  a  species 
with  an  extraordinarily  developed  organ  has  become  the 
parent  of  many  modified  descendants — which  on  our  view 
must  be  a  very  slow  process,  requiring  a  long  lapse  of  time 
— in  this  case,  natural  selection  has  succeeded  in  giving  a 
fixed  character  to  the  organ,  in  however  extraordinary  a 
manner  it  may  have  been  developed.  Species  inheriting 
nearly  the  same  constitution  from  a  common  parent,  and 
exposed  to  similar  influences,  naturally  tend  to  present 
analogous  variations,  or  these  same  species  may  occasionally 
revert  to  some  of  the  characters  of  their  ancient  progeni¬ 
tors.  Although  new  and  important  modifications  may  not 
arise  from  reversion  and  analogous  variation,  such  modi¬ 
fications  will  add  to  the  beautiful  and  harmonious  diver¬ 
sity  of  nature. 

Whatever  the  cause  may  be  of  each  slight  difference  be¬ 
tween  the  offspring  and  their  parents — and  a  cause  for 
each  must  exist — we  have  reason  to  believe  that  it  is  the 
steady  accumulation  of  beneficial  differences  which  has 
given  rise  to  all  the  more  important  modifications  of  struc¬ 
ture  in  relation  to  the  habits  of  each  species. 


158 


DIFFICULTIES  OF  WE  THEORY. 


4 


CHAPTER  VI. 

DIFFICULTIES  OF  THE  THEORY. 

Difficulties  of  the  theory  of  descent  with  modification— Absence  or 
rarity  of  transitional  varieties — Transitions  in  habits  of  life— 
Diversified  habits  in  the  same  species — Species  with  habits 
widely  different  from  those  of  their  allies— Organs  of  extreme 
perfection — Modes  of  transition — Cases  of  difficulty — Natura  non 
facit  saltum — Organs  of  small  importance — Organs  not  in  all 
cases  absolutely  perfect— The  law  of  Unity  of  Type  and  of  the 
Conditions  of  *  Existence  embraced  by  the  theory  of  Natural 
Selection. 

Long  before  the  reader  has  arrived  at  this  part  of  my 
work,  a  crowd  of  difficulties  will  have  occurred  to  him. 
Some  of  them  are  so  serious  that  to  this  day  I  can  hardly 
reflect  on  them  without  being  in  some  degree  staggered; 
but,  to  the  best  of  my  judgment,  the  greater  number  are 
only  apparent,  and  those  that  are  real  are  not,  I  think, 

fatal  to  the  theory.  ’ 

These  difficulties  and  ejections  may  be  classed  under  the 
following  heads:  First,  why,  if  species  have  descended  from 
other  species  by  fine  gradations,  do  we  not  everywhere  see 
innumerable  transitional  forms?  Why  k  not  all  nature  in 
confusion,  instead  of  the  species  being,  as  we  see  them, 

well  defined?  ....  _ 

Secondly,  is  it  possible  that  an  animal  having,  tor 

instance,  the  structure  and  habits  of  a  bat,  could  ha\e  been 
formed  by  the  modification  of  some  other  animal  with 
widely  different  habits  and  structure?  Can  we  believe  that 
natural  selection  could  produce,  on  the  one  hand,  an  organ 
of  trifling  importance,  such  as  the  tail  of  a  giraffe,  which 
serves  as  a  fly-flapper,  and,  on  the  other  hand,  an  oigan  so 
wonderful  as  the  eye? 

Thirdly,  can  instincts  be  acquired  and  modified  through 
natural  selection?  What  shall  we  say  to  the  instinct  which 


DIFFICULTIES  OF  THE  THEORY.  159 

leads  the  bee  to  make  cells,  and  which  has  practically 
anticipated  the  discoveries  of  profound  mathematicians? 

Fourthly,  how  can  we  account  for  species,  when  crossed, 
being  sterile  and  producing  sterile  offspring,  whereas, 
when  varieties  are  crossed,  their  fertility  is  unimpaired? 

The  two  first  heads  will  here  be  discussed;  some  miscel¬ 
laneous  objections  in  the  following  chapter;  Instinct  and 
Hybridism  in  the  two  succeeding  chapters. 

OK  THE  ABSEHCE  OR  RARITY  OF  TRAHSITIOHAL  VARIETIES. 

As  natural  selection  acts  solely  by  the  preservation  of 
profitable  modifications,  each  new  form  will  tend  in  a 
fully-stocked  country  to  take  the  place  of,  and  finally  to 
exterminate,  its  own  less  improved  parent-form  and  other 
less-favored  forms  with  which  it  comes  into  competition. 
Thus  extinction  and  natural  selection  go  hand  in  hand. 
Hence,  if  we  look  at  each  species  as  descended  from  some 
unknown  form,  both  the  parent  and  all  the  transitional 
varieties  will  generally  have  been  exterminated  by  the 
very  process  of  the  formation  and  perfection  of  the  new 
form. 

But,  as  by  this  theory  innumerable  transitional  forms 
must  have  existed,  why  do  we  not  find  them  imbedded 
in  countless  numbers  in  the  crust  of  the  earth?  It 
will  be  more  convenient  to  discuss  this  question  in  the 
chapter  on  the  Imperfection  of  the  Geological  Becord; 
a.n(^  here  only  state  that  I  believe  the  answer  mainly 

lies  in  the  record  being  incomparably  less  perfect  than  is 
generally  supposed.  The  crust  of  the  earth  is  a  vast 
museum;  but  the  natural  collections  have  been  imperfectly 
made,  and  only  at  long  intervals  of  time. 

But  it  may  be  urged  that  when  several  closely  allied 
species  inhabit  the  same  territory,  we  surely  ought  to  find 
at  the  present  time  many  transitional  forms.  Let  us  take 
a  simple  case:  in  traveling  from  north  to  south  over  a  con¬ 
tinent,  we  generally  meet  at  successive  intervals  with 
closely  allied  or  representative  species,  evidently  filling 
nearly  the  same  place  in  the  natural  economy  of  the  land. 
These  representative  species  often  meet  and  interlock;  and 
as  the  one  becomes  rarer  and  rarer,  the  other  becomes  more 
and  more  frequent,  till  the  one  replaces  the  other.  But 


ICO 


ABSENCE  OR  RARITY 


if  we  compare  these  species  where  they  intermingle,  they 
are  generally  as  absolutely  distinct  from  each  other  in  every 
detail  of  structure  as  are  specimens  taken  from  the  metrop¬ 
olis  inhabited  by  each.  By  my  theory  these  allied  species 
are  descended  from  a  common  parent;  and  during  the 
process  of  modification,  each  has  become  adapted  to  the 
conditions  of  life  of  its  own  region,  and  has  supplanted  and 
exterminated  its  original  parent-form  and  all  the  transi¬ 
tional  varieties  between  its  past  and  present  states.  Hence 
we  ought  not  to  expect  at  the  present  time  to  meet  with 
numerous  transitional  varieties  in  each  region,  though  they 
must  have  existed  there,  and  may  be  imbedded  there  in  a 
fossil  condition.  But  in  the  intermediate  region,  having 
intermediate  conditions  of  life,  why  do  we  not  now  find 
closely  linking  intermediate  varieties?  This  difficulty  for 
a  long  time  quite  confounded  me.  But  I  think  it  can  be 
in  large  part  explained. 

In  the  first  place  we  should  be  extremely  cautious  in  in¬ 
ferring,  because  an  area  is  now  continuous,  that  it  has  been 
continuous  during  a  long  period.  Geology  would  lead  us 
to  believe  that  most  continents  have  been  broken  up  into 
islands  even  during  the  later  tertiary  periods;  and  in  such 
islands  distinct  species  might  have  been  separately  formed 
without  the  possibility  of  intermediate  varieties  existing  in 
the  intermediate  zones.  By  changes  in  the  form  of  the 
land  and  of  climate,  marine  areas  now  continuous  must 
often  have  existed  within  recent  times  in  a  far  less  continu¬ 
ous  and  uniform  condition  than  at  present.  But  I  will  pass 
over  this  way  of  escaping  from  the  difficulty;  for  I  believe 
that  many  perfectly  defined  species  have  been  formed  on 
strictly  continuous  areas;  though  I  do  not  doubt  that  the 
formerly  broken  condition  of  areas  now  continuous,  has 
played  an  important  part  in  the  formation  of  new  species, 
more  especially  with  freely-crossing  and  wandering 
animals. 

In  looking  at  species  as  they  are  now  distributed  over  a 
wide  area,  we  generally  find  them  tolerably  numerous  over 
a  large  territory,  then  becoming  somewhat  abruptly  rarer 
and  rarer  on  the  confines,  and  finally  disappearing.  Hence 
the  neutral  territory  between  two  representative  species  is 
generally  narrow  in  comparison  with  the  territory  proper 
to  each.  We  see  the  same  fact  in  ascending  mountains. 


OF  TRANSITION  A  t,  VARIETIES. 


1G1 


and  sometimes  it  is  quite  remarkable  how  abruptly,  as 
Alph.  de  Candolle  has  observed,  a  common  alpine  species 
disappears.  The  same  fact  has  been  noticed  by  E.  Forbes 
in  sounding  the  depths  of  the  sea  with  the  dredge. 
To  those  who  look  at  climate  and  the  physical  conditions 
of  life  as  the  all-important  elements  of  distribution,  these 
facts  ought  to  cause  surprise,  as  climate  and  height  or  depth 
graduate  away  insensibly.  But  when  we  bear  in  mind  that 
almost  every  species,  even  in  its  metropolis,  would  increase 
immensely  in  numbers,  were  it  not  for  other  competing 
species;  that  nearly  all  either  prey  on  or  serve  as  prey  for 
others;  in  short,  that  each  organic  being  is  either  directly 
or  indirectly  related  in  the  most  important  manner  to 
other  organic  beings — we  see  that  the  range  of  the  inhab¬ 
itants  of  any  country  by  no  means  exclusively  depends  on 
insensibly  changing  physical  conditions,  but  in  a  large 
part  on  the  presence  of  other  species,  on  which  it  lives,  or 
by  which  it  is  destroyed,  or  with  which  it  comes  into  com¬ 
petition;  and  as  these  species  are  already  defined  objects, 
not  blending  one  into  another  by  insensible  gradations,  the 
range  of  any  one  species,  depending  as  it  does  on  the  range 
of  others,  will  tend  to  be  sharply  defined.  Moreover,  each 
species  on  the  confines  of  its  range,  where  it  exists  in  les¬ 
sened  numbers,  will,  during  fluctuations  in  the  number  of 
its  enemies  or  of  its  prey,  or  in  the  nature  of  the  seasons, 
be  extremely  liable  to  utter  extermination;  and  thus  its 
geographical  range  will  come  to  be  still  more  sharply 
defined. 

As  allied  or  representative  species,  when  inhabiting  a 
continuous  area,  are  generally  distributed  in  such  a  manner 
that  each  has  a  wide  range,  with  a  comparatively  narrow 
neutral  territory  between  them,  in  which  they  become 
rather  suddenly  rarer  and  rarer;  then,  as  varieties  do  not  es¬ 
sentially.  differ  from  species,  the  same  rule  will  probably 
apply  to  both;  and  if  we  take  a  varying  species  inhabiting  a 
very  large  area,  we  shall  have  to  adapt  two  varieties  to  two 
large  areas,  and  a  third  variety  to  a  narrow  intermediate  zone. 
The  intermediate  variety,  consequently,  will  exist  in  lesser 
numbers  from  inhabiting  a  narrow  and  lesser  area;  and 
practically,  as  far  as  I  can  make  out,  this  rule  holds  good 
with  varieties  in  a  state  of  nature.  I  have  met  with  strik¬ 
ing  instances  of  the  rule  in  the  case  of  varieties  intermediate 


16* 


ABSENCE  OR  RARITY 


between  well-marked  varieties  in  the  genus  Balanus.  And 
it  would  appear  from  information  given  me  by  Mr.  Watson, 
Dr.  Asa  Gray  and  Mr.  Wollaston,  that  generally,  when 
varieties  intermediate  between  two  other  forms  occur,  they 
are  much  rarer  numerically  than  the  forms  which  they  con¬ 
nect.  Now,  if  we  may  trust  these  facts  and  inferences, 
and  conclude  that  varieties  linking  two  other  varieties  to¬ 
gether  generally  have  existed  in  lesser  numbers  than  the 
forms  which  they  connect,  then  we  can  understand  why 
intermediate  varieties  should  not  endure  for  very  long 
periods!  why,  as  a  general  rule,  they  should  be  extei- 
minated  and  disappear,  sooner  than  the  forms  which  they 
originally  linked  together. 

For  any  form  existing  in  lesser  numbers  would,  as  already 
remarked,  run  a  greater  chance  of  being  exterminated 
than  one  existing  in  large  numbers;  and  in  this  particular 
case  the  intermediate  form  would  be  eminently  liable 
to  the  inroads  of  closely  allied  forms  existing  on  both 
sides  of  ito  But  it  is  a  far  more  important  considera¬ 
tion,  that  during  the  process  of  further  modification, 
by  which  two  varieties  are  supposed  to  be  converted 
and  perfected  into  two  distinct  species,  the  two  which 
exist  in  larger  numbers,  from  inhabiting  larger  areas, 
will  have  a  great  advantage  over  the  intermediate 
variety,  which  exists  in  smaller  numbers  in  a.  narrow  and 
intermediate  zone.  For  forms  existing  in  larger  numbers 
will  have  a  better  chance,  within  any  given  period,  of  pre¬ 
senting  further  favorable  variations  for  natural  selection  to 
seize  on,  than  will  the  rarer  forms  which  exist  in  lesser 
numbers.  Hence,  the  more  common  forms,  in  the  race  for 
life,  will  tend  to  beat  and  supplant  the  less  common  forms, 
for  these  will  be  more  slowly  modified  and  improved.  It 
is  the  same  principle  which,  as  I  believe,  accounts  for  the 
common  species  in  each  country,  as  shown  in  the  second 
chapter,  presenting  on  an  average  a  greater  number  of  well- 
marked  varieties  than  do  the  rarer  species.  I  may  illus¬ 
trate  what  I  mean  by  supposing  three  varieties  of  sheep  to 
be  kept,  one  adapted  to  an  extensive  mountainous  region; 
a  second  to  a  comparatively  narrow,  hilly  tract;  and  a 
third  to  the  wide  plains  at  the  base;  and  that  the  inhabi¬ 
tants  are  all  trying  with  equal  steadiness  and  skill  to  im¬ 
prove  their  stocks  by  selection;  the  chances  in  this  case 


OF  TRANSITIONAL  VARIETIES.  163 

will  be  strongly  in  favor  of  the  great  holders  on  the  mount- 
am.s ,  °r  °n  tlile  plains,  improving  their  breeds  more 
quickly  than  the  small  holders  on  the  intermediate  narrow 
hilly  tract;  and  consequently  the  improved  mountain  or 
plain  breed  will  soon  take  the  place  of  the  less  improved 
lull  bleed,  and  thus  the  two  breeds,  which  originally  ex¬ 
isted  in  greater  numbers,  will  come  into  close  contact  with 
each  other,  without  the  interposition  of  the  supplanted,  in¬ 
termediate  hill  variety. 

Po  sum  up,  I  believe  that  species  come  to  be  tolerablv 
well-defined  objects,  and  do  not  at  any  one  period  present 
an  inextricable  chaos  of  varying  and  intermediate  links: 
first,  because  new  varieties  are  very  slowly  formed,  for  vari¬ 
ation  is  a  slow  process,  and  natural  selection  can  do  noth¬ 
ing  until  favorable  individual  differences  or  variations 
occur,  and  until  a  place  in  the  natural  polity  of  the  coun- 
tiy  can  be  bettei  filled  by  some  modification  of  some  one 
01  moie  of  its  inhabitants.  And  such  new  places  will  de¬ 
pend  on  slow  changes  of  climate,  or  on  the  occasional  im¬ 
migration  of  new  inhabitants,  and,  probablv,  in  a  still  more 
important  degree,  on  some  of  the  old  inhabitants  becoming 
slowly  modified,  with  the  new  forms  thus  produced  and 
the  old  ones  acting  and  reacting  on  each  other.  So  that, 
m  any  one  region  and  at  any  one  time,  we  ought  to  see 
only  a  few  species  presenting  slight  modifications  of  struc¬ 
ture  m  some  degree  permanent;  and  this  assuredlv  we  do 
see.  J 

Secondly,  areas  now  continuous  must  often  have  existed 
within  the  recent  period. as  isolated  portions,  in  which 
many  forms,  more  especially  among  the  classes  which 
unite  for  each  birth  and  wander  much,  may  have  sepa¬ 
rately  been  rendered  sufficiently  distinct  to  rank  as  repre¬ 
sentative  species.  In  this  case,  intermediate  varieties  be¬ 
tween  the  se\eial  lepresentative  species  and  their  common 
parent,  must  formerly  have  existed  within  each  isolated 
poition  of  the  land,  but  these  links  during  the  process  of 
natural  selection  will  have  been  supplanted  and  exterm  in- 
ated  so  that  they  will  no  longer  be  found  in  a  living  state. 

.  -thirdly,  when  two  or  more  varieties  have  been  formed 
m  different,  portions  of  a  strictly  continuous  area,  interme¬ 
diate  varieties  will,  it  is  probable,  at  first  have  been  formed 
in  the  intermediate  zones,  but  they  will  generally  have  had 


I(]4  transitions  of  organic  beings. 

a  Short  duration.  For  these  intermediate  varieties  will 
frnm  reasons  already  assigned  (namely  fiom  what 
we  know  of  the  actual  distribution  of  closely  allied 
or  representative  species,  and  likewise  of  acknowl¬ 
edged  varieties),  exist  in  the  intermediate  zones  in  lesser 
numbers  than  the  varieties  which  they  tend  to  connect. 
From  this  cause  alone  the  intermediate  variety  will  be 
li-xble  to  accidental  extermination;  and  during  the  piocess 
of  further  modification  through  natural  selection,  they 
will  almost  certainly  be  beaten  and  supplanted  by  the 
forms  which  tliev  connect;  for  these,  from  existing  in 
greater  numbers/ will,  in  the  aggregate,  present  moie 
varieties,  and  thus  be  further  improved  through  natuial 

selection  and  gain  further  advantages. 

Lastly  looking  not  to  any  one  time,  but  at  all  time,  n 
mv  theory  be  true,  numberless  intermediate  varieties,  lm  - 
inI  closely  together  all  the  species  of  the  same  group,  must 
asfuredly  have  existed;  but  the  very  process  of  natural 
selection  constantly  tends,  as  has  been  so  often  remarked, 
to  exterminate  the  parent-forms  and  the  intermediate  links. 
Consequently  evidence  of  their  former  existence  could  be 
found  among  fossil  remains,  which  are  preserved  as  we 
shah  attempt  to  show  in  a  future  chapter,  in  an  extremely 
imperfect  and  intermittent  record. 

ON  THE  ORIGIN  AND  TRANSITION  OF  ORGANIC  BEINGS 
WITH  PECULIAR  HABITS  AND  STRUCTURE. 

It' has  been  asked  by  the  opponents  of  such  v'ews  as  I 
hold  how,  for  instance,  could  a  land  carnivorous  anim 
have  been  converted  into  one  with  aquatic  habits;  for 
how  could  the  animal  in  its  transitional  state  have  sub¬ 
sisted?  It  would  be  easy  to  show  that  there  now  exis 
carnivorous  animals  presenting  close  intermediate  grades 
from  strictly  terrestrial  to  aquatic  habits;  and  as  each 
exists  by  a  struggle  for  life,  it  is  clear  that  each  must  be 

well  adapted  to  its  place  in  nature  Look  at  f  w and 
vision  of  North  America,  which  has  webbed  ^eet,  and 
which  resembles  an  otter  in  its  fur,  short  legs,  and  for 
of  tail.  During  the  summer  this  animal  dives  for  a 
nrevs  on  fish,  but  during  the  long  winter  it  leaves  the 
frozen  waters,  and  preys,  like  other  pole-cats,  on  mice  and 


TRANSITIONS  OF  ORGANIC  BEINGS. 


165 


land  animals.  If  a  different  case  had  been  taken,  and  it 
had  been  asked  how  an  insectivorous  quadruped  could  pos¬ 
sibly  have  been  converted  into  a  flying  bat,  the  question 
would  have  been  far  more  difficult  to  answer.  Yet  I  think 
such  difficulties  have  little  weight. 

Here,  as  on  other  occasions,  1  lie  under  a  heavy  disad¬ 
vantage,  for,  out  of  the  many  striking  cases  which  I  have 
collected,  I  can  give  only  one  or  two  instances  of  transitional 
habits  and  structures  in  allied  species;  and  of  diversified 
habits,  either  constant  or  occasional,  in  the  same  species. 
And  it  seems  to  me  that  nothing  less  than  a  long  list  of 
such  cases  is  sufficient  to  lessen  the  difficulty  in  any  par¬ 
ticular  case  like  that  of  the  bat. 

Look  at  the  family  of  squirrels;  here  we  have  the  finest 
gradation  from  animals  with  their  tails  only  slightly  flat¬ 
tened,  and  from  others,  as  Sir  J.  Richardson  has  remarked, 
with  the  posterior  part  of  their  bodies  rather  wide  and  with 
the  skin  on  their  flanks  rather  full,  to  the  so-called  flying 
squirrels;  and  flying  squirrels  have  their  limbs  and  even  the 
base  of  the  tail  united  by  a  broad  expanse  of  skin,  which 
serves  as  a  parachute  and  allows  them  to  glide  through  the 
air  to  an  astonishing  distance  from  tree  to  tree.  We  can¬ 
not  doubt  that  each  structure  is  of  use  to  each  kind  of 
squirrel  in  its  own  country,  by  enabling  it  to  escape  birds 
or  beasts  of  prey,  to  collect  food  more  quicklv,  or, 
as  there  is  reason  to  believe,  to  lessen  the  danger  from 
occasional  falls.  But  it  does  not  follow  from  this  fact  that 
the  structure  of  each  squirrel  is  the  best  that  it  is  possible 
to  conceive  under  all  possible  conditions.  Let  the  climate 
and  vegetation  change,  let  other  competing  rodents  or  new 
beasts  of  prey  immigrate,  or  old  ones  become  modified,  and 
all  analogy  would  lead  us  to  believe  that  some,  at  least,  of 
the  squirrels  would  decrease  in  numbers  or  become  exter¬ 
minated,  unless  they  also  become  modified  and  improved 
in  structure  in  a  corresponding  manner.  Therefore,  I  can 
see  no  difficulty,  more  especially  under  changing  conditions 
of  life,  in  the  continued  preservation  of  individuals  with 
fuller  and  fuller  flank-membranes,  each  modification  being 
useful,  each  being  propagated,  until,  by  the  accumulated 
effects  of  this  process  of  natural  selection,  a  perfect  so- 
called  flying  squirrel  was  produced. 

Now  look  at  the  Galeopithecus  or  so-called  flying  lemur. 


TRANSITIONS  OF  ORGANIC  BEINGS. 


106 

which,  was  formerly  ranked  among  hats,  hut  is  now  believed 
to  belong  to  the  Insectivora.  An  extremely  wide  flank- 
membrane  stretches  from  the  corners  of  the  jaw  to  the  tail, 
and  includes  the  limbs  with  the  elongated  fingers.  This 
flank-membrane  is  furnished  with  an  extensor  muscle. 
Although  no  graduated  links  of  structure,  fitted  for 
gliding  through  the  air,  now  connect  the.  Galeopi- 
thecus  with  the  other  Insectivora,  yet  there  is  no  dif¬ 
ficulty  in  supposing  that  such  links  formerly  existed, 
and  that  each  was  developed  in  the  same  manner 
as  with  the  less  perfectly  gliding  squirrels;  each  grade 
of  structure  having  been  useful  to  its  possessor.  Nor 
can  I  see  any  insuperable  difficulty  in  further  believ¬ 
ing  that  the  membrane  connected  fingers  and  forearm  of 
the  Galeopithecus  might  have  been  greatly  lengthened  by 
natural  selection;  and  this,  as  far  as  the  organs  of  .flight 
are  concerned,  would  have  converted  the  animal  into  a 
bat.  In  certain  bats  in  which  the  wing-membrane  extends 
from  the  top  of  the  shoulder  to  the  tail  and  includes  the 
hind-legs,  we  perhaps  see  traces  of  an  apparatus  originally 
fitted  for  gliding  through  the  air  rather  than  for  flight. 

If  about  a  dozen  genera  of  birds  were  to  become  extinct, 
who  would  have  ventured  to  surmise  that  birds  might  have 
existed  which  used  their  wings  solely  as  flappers,  like  the 
logger-headed  duck  (Micropterus  of  Eyton);  as  fins  in  the 
water  and  as  front- legs  on  the  hand,  like  the  penguin;  as 
sails,  like  the  ostrich;  and  functionally  for  no  purpose, 
like  the  apteryx?  Yet  the  structure  of  each  of  these 
birds  is  good  for  it,  under  the  conditions  of  life  to  which 
it  is  exposed,  for  each  has  to  live  by  a  struggle:  but  it  is 
not  necessarially  the  best  possible  under  all  possible  con¬ 
ditions.  It  must  not  be  inferred  from  these  remarks  that 
any  of  the  grades  of  wing-structure  here  alluded  to,  which 
perhaps  may  all  be  the  result  of  disuse,  indicate  the  steps 
by  which  birds  actually  acquired  their  perfect  power  of 
flight;  but  they  serve  to  show  what  diversified  means  of 
transition  are  at  least  possible. 

Seeing  that  a  few  members  of  such  water-breathing 
classes  as  the  Crustacea  and  Mollusca  are  adapted  to  live 
on  the  land;  and  seeing  that  we  have  flying  birds  and 
mammals,  flying  insects  of  the  most  diversified  types,  and 
formerly  had  flying  reptiles,  it  is  conceivable  that  flying- 


TRANSITIONS  OF  ORGANIC  BEINGS ,  16? 

^  which  now  glide  far  through  the  air,  slightly  rising 
and  turning  by  the  aid  of  their  fluttering  fins,  might  have 
been  modified  into  perfectly  winged  animals.  If  this  had 
been  effected,  who  would  have  ever  imagined  that  in  an 
early  transitional  state  they  had  been  the  inhabitants  of 
a'  u^Pen  ocean,  &nd  had  used  their  incipient  organs  of 
flight  exclusively,  so  far  as  we  know,  to  escape  being  de¬ 
voured  by  other  fish? 

^hen  we  see  any  structure  highly  perfected  for  any  par¬ 
ticular  habit,  as  the  wings  of  a  bird  for  flight,  we  should 
beai  in  mind  that  animals  displaying  early  transitional 
giades  of  the  structure  will  seldom  have  survived  to  the 
present  day,  for  they  will  have  been  supplanted  by  their 
successors,  which  were  gradually  rendered  more  perfect 
through  natural  selection.  Furthermore,  we  may  con¬ 
clude  that  transitional  states  between  structures  fitted  for 
veiy  diffeient  habits  of  life  will  rarely  have  been  developed 
at  an  early  period  in  great  numbers  and  under  many  sub¬ 
ordinate  forms.  1  hus,  to  return  to  our  imaginary  illus¬ 
tration  of  the  flying-fish,  it  does  not  seem  probable  that 
nshes  capable  of  true  flight  would  have  been  developed 
under  many  subordinate  forms,  for  taking  prey  of  many 
kinds  m  many  ways,  on  the  land  and  in  the  water,  until 
their  organs  of  flight,  had  come  to  a  high  stage  of  perfec¬ 
tion,  so  as  to  have  given  them  a  decided  advantage  over 
other  animals  in  the  battle  for  life.  Hence  the  chance  of 
discovering  species  with  transitional  grades  of  structure  in 
a  fossil  condition  will  always  be  less,  from  their  having 
existed  in  lesser  numbers,  than  in  the  case  of  species  with 
iully  developed  structures. 

I  will  now  give  two  or  three  instances,  both  of  diversified 
and .  of  changed  habits,  in  the  individuals  of  the  same 
species.  In  either  case  it  would  be  easy  for  natural  selec¬ 
tion  to  adapt  the  structure  of  the  animal  to  its  changed 
habits,  or  exclusively  to.  one  of  its  several  habits.  It  is, 
however,  difficult  to  decide  and  immaterial  for  us,  whether 
habits  generally  change  first  and  structure  afterward;  or 
whether  slight  modifications  of  structure  lead  to  changed 
habits;  both  probably  often  occurring  almost  simultane¬ 
ously.  Of  cases  of  changed  habits  it  will  suffice  merely  to 
allude  to  that  of  the  many  British  insects  which  now  feed 
on  exotic  plants,  or  exclusively  on  artificial  substances. 


168 


TRANSITIONS  OF  ORGANIC  BEINGS. 


Of  diversified  habits  innumerable  instances  could  be  given: 
I  have  often  watched  a  tyrant  flycatcher  (Saurophagus  sul- 
phuratus)  in  South  America,  hovering  over  one  spot  and 
then  proceeding  to  another,  like  a  kestrel,  and  at  other 
times  standing  stationary  on  the  margin  of  water,  and  then 
dashing  into  it  like  a  kingfisher  at  a  fish.  In  our  own 
country  the  larger  titmouse  (Parus  major)  may  be  seen 
climbing  branches,  almost  like  a  creeper;  it  sometimes, 
like  a  shrike,  kills  small  birds  by  blows  on  the  head;  and  I 
have  many  times  seen  and  heard  it  hammering  the  seeds  of 
the  yew  on  a  branch,  and  thus  breaking  them  like  a  nut¬ 
hatch.  In  North  America  the  black  bear  was  seen  by 
Hearne  swimming  for  hours  with  widely  open  mouth,  thus 
catching,  almost  like  a  whale,  insects  in  the  water. 

As  we  sometimes  see  individuals  following  habits  differ¬ 
ent  from  those  proper  to  their  species  and  to  the  other 
species  of  the  same  genus,  we  might  expect  that  such  in¬ 
dividuals  would  occasionally  give  rise  to  new  species, 
having  anomalous  habits,  and  with  their  structure 
either  slightly  or  considerably  modified  from  that  of  their 
type.  And  such  instances  occur  in  nature.  Can  a  more 
striking  instance  of  adaptation  be  given  than  that  of 
a  woodpecker  for  climbing  trees  and  seizing  insects  in  the 
chinks  of  the  bark?  Yet  in  North  America  there  are 
woodpeckers  which  feed  largely  on  fruit,  and  others 
with  elongated  wings  which  chase  insects  on  the  wing. 
On  the  plains  of  La  Plata,  where  hardly  a  tree  grows, 
there  is  a  woodpecker  ( Colap tes  campestris)  which  has  two 
toes  before  and  two  behind,  a  long-pointed  tongue,  pointed 
tail-feathers,  sufficiently  stiff  to  support  the  bird  in  a  verti¬ 
cal  position  on  a  post,  but  not  so  stiff  as  in  the  typical  wood¬ 
peckers,  and  a  straight,  strong  beak.  The  beak,  however, 
is  not  so  straight  or  so  strong  as  in  the  typical  woodpeckers 
but  it  is  strong  enough  to  bore  into  wood.  Hence  this 
Colaptes,  in  all  the  essential  parts  of  its  structure,  is  a  wood¬ 
pecker.  Even  in  such  trifling  characters  as  the  coloring, 
the  harsh  tone  of  the  voice,  and  undulatory  flight,  its  close 
blood-relationship  to  our  common  woodpecker  is  plainly 
declared;  yet,  as  I  can  assert,  not  only  from  my  own  ob¬ 
servations,  but  from  those  of  the  accurate  Azara,  in  certain 
large  districts  it  does  not  climb  trees,  and  it  makes  its 
nest  in  holes  in  banks!  In  certain  other  districts,  however, 


transitions  of  organic  BEING  is. 


169 


this  same  woodpecker,  as  Mr.  Hudson  states,  frequents 
trees  and  bores  holes  in  the  trunk  for  its  nest.  I 
mention  as  another  illustration  of  the  varied  habits  of 
genus,  that  a  Mexican  Colaptes  has  been  described  by  De 

Stor:SofreacornsnnS  68  ^  hard  W°°d  in  0rdei' to  la/“P  a 

.  Petrels  .a[e  the  most  aerial  and  oceanic  of  birds  but 
m  the  quiet  sounds  of  Tierra  del  Fuego,  the  Puffinuria 
beiardi,  in  its  general  habits,  in  its  astonishing  power  of 
diving  m  i  s  manner  of  swimming  and  of  flying  when 
made  to  take  flight,  would  be  mistaken  b/ any  one 

„  t  a,n  J.r,, a  Srebe;  nevertheless  it  is  essentially  a 
petiel,  but  with  many  parts  of  its  organization  pro- 

wWd  7  ,?lodlfled  ln,  relation  to  its  new  habits  of  life- 
whereas  the  woodpecker  of  La  Plata  has  had  its  structure 
on  y  slightly  modified.  In  the  case  of  the  water-ouzel 
the  acutest  observer,  by  examining  its  dead  body,  would 
ever  have  suspected  its  sub-aquatic  habits;  yet  this  bird 
which  is  allied  to  the  thrush  family,  subsists  by  divine- 

fee^ S  lVZglZler  Wafte+n  and  gasping  stones  with°its 
teet.  All  the  members  of  the  great  order  of  Hvmenonter 

oils  insects  are  terrestrial,  excepting  the  genuT Pronto 
rupes  which  Sir  John  Lubbock  ifas  discovered  to  be' 
acquatic  in  its  habits;  it  often  enters  the  water  and  dives 
about  by  the  use  not  of  its  legs  but  of  its  wings,  and  re¬ 
mains  as  long  as  four  hours  beneath  the  surface-  vet  it 

SSiZSlt110" in 

as  met  with  an  animal  having  habits  and  structure  not  in 

fETnfT'Y  W  !,at  Can  be  Plainer  than  that  the  webbed 
eet  of  ducks  and  geese  are  formed  for  swimming?  Yet 

nesr6  fh®  l'Piaild  g®?Se  with  webbed  feet  which  rarely  go 
near  the  water;  and  no  one,  except  Audubon,  has  sefn 

on  thogater  blrd%Willch  has  a11  lts  four  toes  webbed,  alight 
on  the  surface  of  the  ocean.  On  the  other  hand  grebes 

onh  W  S  “a®  ®mmen%  aquatic,  although  their  toes  are 

thlt  Z  ?ed  r7  membrane-.  What  seems  plainer  than 
that  the  long  toes,  not  furnished  with  membrane  of  the 

ing  plants8?  f  f?r  walk'ng  over  swamps  and  float¬ 

ing  plants.?  The  water-lieu  and  landrail  are  members  of 


170 


ORGANS  OF  EXTREME  PERFECTION. 


this  order,  yet  the  first  is  nearly  as  aquatic,  as  the  coot,  and 
the  second  is  nearly  as  terrestrial  as  the  quail  or  partridge. 
In  such  cases,  and  many  others  could  be  given,  habits  have 
changed  without  a  corresponding  change  of  structure.  The 
webbed  feet  of  the  upland  goose  may  be  said  to  have  be¬ 
come  almost  rudimentary  in  function,  though  not  in  struc¬ 
ture.  In  the  frigate-bird,  the  deeply  scooped  membrane 
between  the  toes  shows  that  structure  has  begun  to  change. 

He  who  believes  in  separate  and  innumerable  acts  of 
creation  may  say,  that  in  these  cases  it  has  pleased  the 
Creator  to  cause  a  being  of  one  type  to  take  the  place  of  one 
belonging  to  another  type;  but  this  seems  to  me  only  re¬ 
stating  the  fact  in  dignified  language.  He  who  believes  in 
the  struggle  for  existence  and  in  the  principle  of  natural 
selection,  will  acknowledge  that  every  organic  being  is  con¬ 
stantly  endeavoring  to  increase  in  numbers;  and  that  if 
any  one  being  varies  ever  so  little,  either  in  habits  or  struc¬ 
ture,  and  thus  gains  an  advantage  over  some  other  inhab¬ 
itant  of  the  same  country,  it  will  seize  on  the  place  of  that 
inhabitant,  however  different  that  may  be  from  its  own 
place.  Hence  it  will  cause  him  no  surprise  that  there  should 
be  geese  and  frigate-birds  with  webbed  feet,  living  on  the 
dry  land  and  rarely  alighting  on  the  water,  that  there 
should  be  long-toed  corncrakes,  living  in  meadows  instead 
of  in  swamps;  that  there  should  be  woodpeckers  where 
hardly  a  tree  grows;  that  there  should  be  diving  thrushes 
and  diving  Hymenoptera,  and  petrels  with  the  habits  of 
auks. 

ORGAN'S  OF  EXTREME  PERFECTION  AND  COMPLICATION. 

To  suppose  that  the  eye  with  all  its  inimitable  contri¬ 
vances  for  adjusting  the  focus  to  different  distances,  for 
admitting  different  amounts  of  light,  and  for  the  correction 
of  spherical  and  chromatic  aberration,  could  have  been 
formed  by  natural  selection,  seems,  I  freely  confess, 
absurd  in  the  highest  degree.  When  it  was  first  said  that 
the  sun  stood  still  and  the  world  turned  round,  the  com¬ 
mon  sense  of  mankind  declared  the  doctrine  false;  but  the 
old  saying  of  Vox  popali,  vox  Dei,  as  every  philosopher 
knows,  can  not  be  trusted  in  science.  Reason  tells  me, 
that  if  numerous  gradations  from  a  simple  and  imperfect 


ORGANS  OF  EXTREME  PERFECTION. 


171 


eye  to  one  complex  and  perfect  can  be  shown  to  exist,  each 
grade  being  useful  to  its  possessor,  as  is  certainly  the  case; 
if  further,  the  eye  ever  varies  and  the  variations  be  in¬ 
herited,  as  is  likewise  certainly  the  case;  and  if  such  varia¬ 
tions  should  be  useful  to  any  animal  under  changing  con¬ 
ditions  of  life,  then  the  difficulty  of  believing  that  a  per¬ 
fect  and  complex  eye  could  be  formed  by  natural  selection, 
though  insuperable  by  our  imagination,  should  not  be  con¬ 
sidered  as  subversive  of  the  theory.  How  a  nerve  comes  to 
be  sensitive  to  light,  hardly  concerns  us  more  than  how  life 
itself  originated;  but  I  may  remark  that,  as  some  of  the  low¬ 
est  organisms  in  which  nerves  can  not  be  detected,  are 
capable  of  perceiving  light,  it  does  not  seem  impossible  that 
certain  sensitive  elements  in  their  sarcode  should  become 
aggregated  and  developed  into  nerves,  endowed  with  this 
special  sensibility. 

In  searching  for  the  gradations  through  which  an  organ  in 
any  species  has  been  perfected,  we  ought  to  look  exclusively 
to  its  lineal  progenitors;  but  this  is  scarcely  ever  possible, 
and  we  are  forced  to  look  to  other  species  and  genera  of  the 
same  group,  that  is  to  the  collateral  descendants  from  the 
same  parent-form,  in  order  to  see  what  gradations 
aie  possible,  and  for  the  chance  of  some  gradations  ha  vino" 
been  transmitted  in  an  unaltered  or  little  altered  condition. 
But  the  state  of  the  same  organ  in  distinct  classes  may  in¬ 
cidentally  throw  light  on  the  steps  by  which  it  has  been 
perfected. 

I  he  simplest  organ  which  can  be  called  an  eye  consists 
of  an  optic  nerve,  surrounded  by  pigment-cells  and  covered 
by  translucent  skin,  but  without  any  lens  or  other  refract¬ 
ive  body.  We  may,  however,  according  to  M.  Jourdain, 
descend  even  a  step  lower  and  find  aggregates  of  pigment- 
cells,  apparently  serving  as  organs  of  vision,  without  any 
nerves,  and  resting  merely  on  sarcodic  tissue.  Eyes  of  the 
above  simple  nature  are  not  capable  of  distinct  vision, 
and  serve  only  to  distinguish  light  from  darkness.  In 
certain  star-fishes,  small  depressions  in  the  layer  of  pig- 
ment  which  surrounds  the  nerve  are  filled,  as  described  by 
the  author  just  quoted,  with  transparent  gelatinous  matter, 
projecting  with  a  convex  surface,  like  the  cornea  in  the 
higher  animals.  He  suggests  that  this  serves  not  to  form 
an  image,  but  only  to  concentrate  the  luminous  rays  and 


172  ORGANS  OF  EXTREME  PERFECTION. 

render  their  perception  more  easy.  In  this  concentration 
of  the  rays  we  gain  the  first  and  by  far  the  most  important 
step  toward  the  formation  of  a  true,  picture-forming  eye; 
for  we  have  only  to  place  the  naked  extremity  of  the  optic; 
nerve,  which  in  some  of  the  lower  animals  lies  deeply 
buried  in  the  body,  and  in  some  near  the  surface,  at  the 
right  distance  from  the  concentrating  apparatus,  and  an 
image  will  be  formed  on  it. 

In  the  great  class  of  the  Articulata,  we  may  start  from 
an  optic  nerve  simply  coated  with  pigment,  the  latter  some¬ 
times  forming  a  sort  of  pupil,  but  destitute  of  lens  or 
other  optical  contrivance.  With  insects  it  is  now  known 
that  the  numerous  facets  on  the  cornea  of  their  great  com¬ 
pound  eyes  form  true  lenses,  and  that  the  cones  include 
curiously  modified  nervous  filaments.  But  these  organs  in 
the  Articulata  are  so  much  diversified  that  Muller  formerly 
made  three  main  classes  with  seven  subdivisions,  besides  a 
fourth  main  class  of  aggregated  simple  eyes. 

When  we  reflect  on  these  facts,  here  given  much  too 
briefly,  with  respect  to  the  wide,  diversified,  and  graduated 
range  of  structure  in  the  eyes  of  the  lower  animals;  and 
when  we  bear  in  mind  how  small  the  number  of  all  living 
forms  must  be  in  comparison  with  those  which  have 
become  extinct,  the  difficulty  ceases  to  be  very  great  in 
believing  that  natural  selection  may  have  converted  the 
simple  apparatus  of  an  optic  nerve,  coated  with  pigment 
and  invested  by  transparent  membrane,  into  an  optical 
instrument  as  perfect  as  is  possessed  by  any  member  of  the 
Articulata  class. 

He  who  will  go  thus  far,  ought  not  to  hesitate  to  go 
one  step  further,  if  he  finds  on  finishing  this  volume 
that  large  bodies  of  facts,  otherwise  inexplicable,  can  be 
explained  by  the  theory  of  modification  through  natural 
selection;  he  ought  to  admit  that  a  structure  even  as 
perfect  as  an  eagle's  eye  might  thus  be  formed,  although 
in  this  case  he  does  not  know  the  transitional  states.  It 
has  been  objected  that  in  order  to  modify  the  eye 
and  still  preserve  it  as  a  perfect  instrument,  many 
changes  would  have  to  be  effected  simultaneously,  which, 
it  is  assumed,  could  not  be  done  through  natural 
selection;  but  as  I  have  attempted  to  show  in  my 
work  on  the  variation  of  domestic  animals,  it  is  not 


ORGANS  OF  EXTREME  PER FEOTIO X.  \  73 

necessary  to  suppose  that  the  modifications  were  all 
simultaneous,  if  they  were  extremely  slight  and  gradual. 
Different  kinds  of  modification  would,  also,  serve  for  the 
same  general  purpose:  as  Mr.  Wallace  has  remarked  “If 
a  len  has  too  short  or  too  long  a  focus,  it  may  be  amended 
eithei  by  an  alteration  of  curvature,  or  an  alteration  of 
density;  if  the  curvature  be  irregular,  and  the  rays  do  not 
converge  to  a  point,  then  any  increased  regularity  of  curva- 
ture  will  be  an  improvement.  So  the  contraction  of  the 
111s  and  the  muscular  movements  of  the  eye  are  neither  of 

to  vision,  but  only  improvements  which 
might  have  been  added  and  perfected  at  any  stage  of  the 
construction  of  the  instrument.”  Within  the  highest 
division  of  the  animal  kingdom,  namely,  the  Vertebrata, 

fri)mr?S  eye  f  simPle>  that  H  consists,  as  in 
the  lancelet,  of  a  little  sack  of  transparent  skin,  furnished 

with  a  nerve  and  lined  with  pigment,  but  destitute  of  any 
other  apparatus.  In  fishes  and  reptiles,  as  Owen  has  re- 
marked,  I  he  range  of  gradation  of  dioptric  structures 
is  very  great  It  is  a  significant  fact  that  even  in  man 
according  to  the  high  authority  of  Virchow,  the  beautiful 
crystalline  lens  is  formed  m  the  embryo  by  an  accumula¬ 
tion  of  epidermic  cells,  lying  in  a  sack-like  fold  of  the  skin- 
and  the  vitreous  body  is  formed  from  embryonic  sub¬ 
cutaneous  tissue.  To  arrive,  however,  at  a  just  conclusion 
regarding  the  formation  of  the  eye,  with  all  its  marvellous 
absolute]y  perfect  characters,  it  is  indispensable 
that  the  reason  should  conquer  the  imagination;  but  I 
have  felt  the  difficulty  far  too  keenly  to  be  surprised  at 
others  hesitating  to  extend  the  principle  of  natural  selec¬ 
tion  to  so  startling  a  length. 

It  is  scarcely  possible  to  avoid  comparing  the  eye  with 
a  telescope  We  know  that  this  instrument  has  been  per- 
fected  by  the  long-continued  efforts  of  the  highest  human 
intellects,  and  we  naturally  infer  that  the  eye  has  been 
iormed  by  a  somewhat  analogous  process.  But  may  not 
this  inference  be  presumptuous?  Have  we  any  right  to 
assume  that  the  Creator  works  by  intellectual  powers  like 
those  of  man.  If  we  must  compare  the  eye  to  an  optical 
instrument,  we  ought  m  imagination  to  take  a  thick  layer 
ot  transparent  tissue,  with  spaces  filled  with  fluid  and 
with  a  nerve  sensitive  to  light  beneath,  and  then  suppose 


MODES  OF  TRANSITION . 


174 

every  part  of  this  layer  to  be  continually  changing  slowly 
in  density,  so  as  to  separate  into  layers  of  diffeient  densi» 
ties  and  thicknesses,  placed  at  different  distances  from  each 
other,  and  with  the  surfaces  of  each  layer  slowly  changing 
in  form.  Further  we  must  suppose  that  there  is  a  power, 
represented  by  natural  selection  or  the  suivival  of  the 
fittest,  always  intently  watching  each  slight  alteration  in 
the  transparent  layers;  and  carefully  preserving  each 
which,  under  varied  circumstances,  in  any  way  or  degree, 
tends  to  produce  a  distincter  image.  We  must  suppose 
each  new  state  of  the  instrument  to  be  multiplied  by  the 
million;  each  to  be  preserved  until  a  better  one  is  pro¬ 
duced,  and  then  the  old  ones  to  be  all  destroyed.  In 
living  bodies,  variation  will  cause  the  slight  alteration, 
generation  will  multiply  them  almost  infinitely,  and  natural 
selection  will  pick  out  with  unerring  skill  each  improve¬ 
ment.  Let  this  process  go  on  for  millions  of  years;.  and 
during  each  year  on  millions  of  individuals  of  many  kinds; 
and  mav  we  not  believe  that  a  living  optical  instrument 
might  thus  be  formed  as  superior  to  one  of  glass,  as  the 
works  of  the  Creator  are  to  those  of  man? 

MODES  OF  TRANSITION. 

If  it  could  be  demonstrated  that  any  complex  organ  ex¬ 
isted,  which  could  not  possibly  have  been  foimed  by  nu¬ 
merous,  successive,  slight  modifications,  my  tlieoiy  would 
absolutely  break  down.  But  I  can  find  out  no  such  case. 
No  doubt  many  organs  exist  of  which  we  do  not  know  the 
transitional  grades,  more  especially  if  we  look  to  much- 
isolated  species,  around  which,  according  to  the  theory, 
there  has  been  much  extinction.  Or  again,  if  we  take  an 
organ  common  to  all  the  members  of  a  class,  for  in  this 
latter  case  the  organ  must  have  been  originally  formed  at 
a  remote  period,  since  which  all  the  many  members  of  the 
class  have  been  developed;  and  in  order  to  discover  the 
early  transitional  grades  through  which  the  organ  has 
passed,  we  should  have  to  look  to  very  ancient  ancestral 

forms,  long  since  become  extinct. 

We  should  be  extremely  cautious  in  concluding  that  an 
organ  could  not  have  been  formed  by  transitional  grada¬ 
tions  of  some  kind.  Numerous  cases  could  be  given 


MODE'S  OF  TRANSITION. 


175 


among  the  lower  animals  of  the  same  organ  performing  at 
the  same  time  wholly  distinct  functions;  thus  in  the  larva 
of  the  ca  agon-fly  and  in  the  fish  Cobites  the  alimentary 
canal  respires,  digests  and  excretes.  In  the  Hydra,  the 
animal  may  be  turned  inside  out,  and  the  exterior  surface 
will  then  digest  and  the  stomach  respire.  In  such  cases 
natural  selection  might  specialize,  if  any  advantage  were 
thus  gained,  the  whole  or  part  of  an  organ,  which  had 
previously  performed,  two  .  functions,  for  one  function 
alone,  and  thus  by  insensible  steps  greatly  change  its 
nature,  IVIany  plants  are  known  which  regularly  produce 
at  the  same  time  differently  constructed  flowers;  and  if 
such  plants  were  to  produce  one  kind  alone,  a  great  change 
would,  be  effected  with  comparative  suddenness  in  the 
character  of  the  species.  It  is,  however,  probable  that  the 
two  sorts  of  flowers  borne  by  the  same  plant  were  originally 
differentiated  by  finely  graduated  steps,  which  may  still 
be  followed  in  some  few  cases. 

Again,  two  distinct  organs,  or  the  same  organ  under  two 
very  different  forms,  may  simultaneously  perform  in  the 
same  individual  the  same  function,  and  this  is  an  extremely 
important  .means  of  transition:  to  give  one  instance — there 
are  fish  with  gills  or  branchia?  that  breathe  the  air  dis¬ 
solved  in  the  water,  at  the  same  time  that  they  breathe 
free  air  in  their  swim-bladders,  this  latter  organ  being 
divided  by  highly  vascular  partitions  and  having  a  ductus 
pneumaticus  for  the  supply  of  air.  To  give  another  in¬ 
stance  from  the  vegetable  kingdom:  plants  climb  by  three 
distinct  means,,  by  spirally  twining,  by  clasping  a  support 
with  their  sensitive  tendrils,  and  by  the  emission  of  aerial 
rootlets;  these  three  means  are  usually  found  in  distinct 
groups,  but  some  few  species  exhibit  two  of  the  means,  or 
even  all  three,  combined  in  the  same  individual.  In  all 
such  cases  one  of  the  two  organs  might  readily  be  modified 
and  perfected  so  as  to  perform  all  the  work,  being  aided 
during  the  progress  of  modification  by  the  other  organ; 
and  then  this  other  organ  might  be  modified  for  some 
other  and  quite  distinct  purpose,  or  be  wholly  obliterated. 

The  illustration  of  the  swim-bladder  in  fishes  is  a 
good  one,  because  it  shows  us  clearly  the  highly 
important  fact  that  an  organ  originally  constructed  for 
one  purpose,  namely,  flotation,  may  be  converted  into 


176  '  MODES  OF  TRANSITION. 

one  for  a  widely  different  purpose,  namely,  respiration. 
The  swim-bladder  has,  also,  been  worked  in  as  an  accessory 
to  the  auditory  organs  of  certain  fishes.  All  physiologists 
admit  that  the  swim-bladder  is  homologous,  or  “  ideally 
similar  ”  in  position  and  structure  with  the  longs  of  the 
higher  vertebrate  animals:  hence  there  is  no  reason  to 
doubt  that  the  swim-bladder  has  actually  been  converted 
into  lungs,  or  an  organ  used  exclusively  for  respiration. 

According  to  this  view  it  may  be  inferred  that  all  verte¬ 
brate  animals  with  true  lungs  are  descended  by  ordinary 
generation  from  an  ancient  and  unknown  prototype,  whirl 
was  furnished  with  a  floating  apparatus  or  swim  bladder. 
We  can  thus,  as  I  infer  from  Owen’s  interesting  descrip¬ 
tion  of  these  parts,  understand  the  strange  fact  that  every 
particle  of  food  and  drink  which  we  swallow  has  to  pass 
over  the  orifice  of  the  trachea,  with  some  risk  of  falling 
into  the  lings,  notwithstanding  the  beautiful  contrivance 
by  which  tho  glottis  is  closed.  In  the  higher  Vertebrata 
the  branchke  have  wholly  disappeared — but  in  the  embryo 
the  slits  on  the  sides  of  the  neck  and  the  loop-like  course 
of  the  arteries  still  mark  their  former  position.  But  it  is 
conceivable  that  the  now  utterly  lost  branchiae  might  have 
been  gradually  worked  in  by  natural  selection  for  some  dis¬ 
tinct  purpose:  for  instance,  Landois  has  shown  that  the 
wings  of  insects  are  developed  from  the  trachea;  it  is  there¬ 
fore"  highly  probable  that  in  this  great  class  organs  which 
once  served  for  respiration  have  been  actually  converted 
into  organs  for  flight. 

In  considering  transitions  of  organs,  it  is  so  important  to 
bear  in  mind  the  probability  of  conversion  from  one  func¬ 
tion  to  another,  that  I  will  give  another  instance.  Pedun¬ 
culated  cirripedes  have  two  minute  folds  of  skin,  called  by 
me  the  ovigerous  frena,  which  serve,  through  the  means  of 
a  sticky  secretion,  to  retain  the  eggs  until  they  are  hatched 
within  the  sack.  These  cirripedes  have  no  branchiae,  the 
whole  surface  of  the  body  and  of  the  sack,  together  with 
the  small  frena,  serving  for  respiration.  The  Balanidae  or 
sessile  cirripedes,  on  the  other  hand,  have  no  ovigerous 
frena,  the  eggs  lying  loose  at  the  bottom  of  the  sack, 
within  the  well-inclosed  shell;  but  they  have,  in  the  same 
relative  position  with  the  frena,  large,  much-folded  mem¬ 
branes,  which  freely  communicate  with  the  circulatory 


MODES  OF  TRANSITION, \ 


177 

lacunae  of  the  sack  and  body,  and  which  have  been  consid¬ 
ered  by  all  naturalists  to  act  as  branchiae.  Now  I  think  no 
one  will  dispute  that  the  o viperous  frena  in  the  one  family 
are  strictly  homologous  with  the  branchiae  of  the  other 
family;  indeed,  they  graduate  into  each  other.  Therefore 
it  need  not  be  doubted  that  the  two  little  folds  of  skin, 
which  originally  served  as  ovigerous  frena,  but  which,  like¬ 
wise,  very  slightly  aided  in  the  act  of  respiration,  have 
been  gradually  converted  by  natural  selection  into  branchiae, 
simply  through  an  increase  in  their  size  and  the  obliteration 
of  their  adhesive  glands.  If  all  pedunculated  cirripedes 
had  become  extinct,  and  they  have  suffered  far  more  extinc¬ 
tion  than  have  sessile  cirripedes,  who  would  ever  have  im¬ 
agined  that  the  branchiae  in  this  latter  family  had  origin¬ 
ally  existed  as  organs  for  preventing  the  ova  from  being 
washed  out  of  the  sack? 

There  is  another  possible  mode  of  transition,  namely, 
through  the  acceleration  or  retardation  of  the  period  of  re¬ 
production.  This  has  lately  been  insisted  on  by  Professor 
Cope  and  others  in  the  United  States.  It  is  now  known 
that  some  animals  are  capable  of  reproduction  at  a  very 
early  age,  before  they  have  acquired  their  perfect  charac¬ 
ters;  and  if  this  power  became  thoroughly  well  developed 
in  a  species,  it  seems  probable  that  the  adult  stage  of  devel¬ 
opment  would  sooner  or  later  be  lost;  and  in  this  case, 
especially  if  the  larva  differed  much  from  the  mature  form, 
the  character  of  the  species  would  be  greatly  changed  and 
degraded.  Again,  not  a  few  animals,  after  arriving  at 
maturity,  go  on  changing  in  character  during  nearly  their 
whole  lives.  With  mammals,  for  instance,  the  form  of  the 
skull  is  often  much  altered  with  age,  of  which  Ur.  Mu.rie 
has  given  some  striking  instances  with  seals.  Every  one 
knows  how  the  horns  of  stags  become  more  and  more 
branched,  and  the  plumes  of  some  birds  become  more  finely 
developed,  as  they  grow  older.  Professor  Cope  states  that 
the  teeth  of  certain  lizards  change  much  in  shape  with  ad¬ 
vancing  years.  With  crustaceans  not  only  many  trivial, 
but  some  important  parts  assume  a  new  character,  as  re¬ 
corded  by  Fritz  Muller,  after  maturity.  In  all  such  cases 
and  many  could  be  given — if  the  age  for  reproduction 
were  retarded,  the  character  of  the  species,  at  least  in  its 
adult  state,  would  be  modified;  nor  is  it  improbable  that 


178  DIFFICULTIES  OF  THE  ’THEORY 

the  previous  and  earlier  stages  of  development  would  in 
some  cases  be  hurried  through  and  finally  lost.  Whether 
species  have  often  or  ever  been  modified  through  this  com¬ 
paratively  sudden  mode  of  transition,  I  can  form  no 
opinion;  but  if  this  has  occurred,  it  is  probable  that  the 
differences  between  the  young  and  the  mature,  and  be¬ 
tween  the  mature  and  the  old,  were  primordially  acquired 
by  graduated  steps. 

SPECIAL  DIFFICULTIES  OF  THE  THEORY  OF  NATURAL 

SELECTION. 

Although  we  must  be  extremely  cautious  in  concluding 
that  any  organ  could  not  have  been  produced  by  successive, 
small,  transitional  gradations,  yet  undoubtedly  serious 
cases  of  difficulty  occur. 

One  of  the  most  series  is  that  of  neuter  insects,  which 
are  often  differently  constructed  from  either  the  males  or 
fertile  females;  but  this  case  will  be  treated  of  in  the  next 
chapter.  The  electric  organs  of  fishes  offer  another  case 
of  special  difficulty,  for  it  is  impossible  to  conceive  by  what 
steps  these  wondrous  organs  have  been  produced.  But 
this  is  not  surprising,  for  we  do  not  even  know  of  what 
use  they  are.  In  the  gymnotus  and  torpedo  they  no  doubt 
serve  as  powerful  means  of  defense,  and  perhaps  for  secur¬ 
ing  prey;  yet  in  the  ray,  as  observed  by  Matteiicc^  an 
analogous  organ  in  the  tail  manifests  but  little  electricity, 
even  when  the  animal  is  greatly  irritated;  so  little  that  it 
can  hardly  be  of  any  use  for  the  above  purposes.  More¬ 
over,  in  the  ray,  besides  the  organ  just  referred  to,  there 
is,  as  Dr.  R.  McDonnell  has  shown,  another  organ  near 
the  head,  not  known  to  be  electrical,  but  which  appears  to 
be  the  real  homologue  of  the  electric  battery  in  the  tor¬ 
pedo.  It  is  generally  admitted  that  there  exists  between 
these  organs  and  ordinary  muscle  a  close  analogy,  in  inti¬ 
mate  structure,  in  the  distribution  of  the  nerves,  and  in 
the  manner  in  which  they  are  acted  on  by  various  reagents. 
It  should,  also,  be  especially  observed  that  muscular  con¬ 
traction  is  accompanied  by  an  electrical  discharge;  and,  as 
Dr.  Radcliffe  ’ insists!  1 of  the 
torpedo  during  rest,  there  would  seem  to  be  a  charge  in 
every  respect  like  that  which  is  met  with  in  muscle  and 


OF  NATURAL  SELECTION, . 


179 

nerve  during  the  rest,  and  the  discharge  of  the  torpedo, 
instead  of  being  peculiar,  may  be  only  another  form  of  the 
discharge  which  attends  upon  the  action  of  muscle  and 
motor  nerve.”  Beyond  this  we  cannot  at  present  go  in  the 
wav  of  explanation;  but  as  we  know  so  little  about  the  uses 
of  these  organs,  and  as  we  know  nothing  about  the  habits 
and  structure  of  the  progenitors  of  the  existing  electric 
fishes,  it  would  be  extremely  bold  to  maintain  that  no 
serviceable  transitions  are  possible  by  which  these  organs 
might  have  been  gradually  developed. 

These  organs  appear  at  first  to  offer  another  and  far 
more  serious  difficulty;  for  they  occur  in  about  a  dozen 
kinds  of  fish,  of  which  several  are  widely  remote  in  their 
affinities.  When  the  same  organ  is  found  in  several  mem¬ 
bers  of  the  same  class,  especially  if  in  members  having 
very  different  habits  of  life,  we  may  generally  attribute  its 
presence  to  inheritance  from  a  common  ancestor;  and  its 
absence  in  some  of  the  members  to  loss  through  disuse  or 
natural  selection.  So  that,  if  the  electric  organs  had  been 
inherited  from  some  one  ancient  progenitor,  we  might  have 
expected  that  all  electric  fishes  would  have  been  specially 
related  to  each  other;  but  this  is  far  from  the  case.  Nor 
does  geology  at  all  lead  to  the  belief  that  most  fishes  for¬ 
merly  possessed  electric  organs,  which  their  modified 
descendants  have  now  lost.  But  when  we  look  at  the  sub¬ 
ject  more  closely,  we  find  in  the  several  fishes  provided  with 
electric  organs,  that  these  are  situated  in  different  parts  of 
the  body,  that  they  differ  in  construction,  as  in  the 
arrangement  of  the  plates,  and,  according  to  Pacini,  in  the 
process  or  means  by  which  the  electricity  is  excited — and 
lastly,  in  being  supplied  with  nerves  proceeding  from  dif¬ 
ferent  sources,  and  this  is  perhaps  the  most  important  of 
all  the  differences.  Hence  in  the  several  fishes  furnished 
with  electric  organs,  these  cannot  be  considered  as  hom¬ 
ologous,  but  only  as  analogous  in  function.  Consequently 
there  is  no  reason  to  suppose  that  they  have  been  inherited 
from  a  common  progenitor;  for  had  this  been  the  case  they 
would  have,  closely  resembled  each  other  in  all  respects. 
Thus  the  difficulty  of  an  organ,  apparently  the  same,  aris¬ 
ing  in  several  remotely  allied  species,  disappears,  leaving 
«>  y  still  great  difficulty:  namely,  by  what 

graduated  steps  these  organs  have  been  developed  in  each 
separate  group  of  fishes. 


180 


DIFFICULTIES  OF  TIIE  THEORY 


The  luminous  organs  which  occur  in  a  few  insects, 
belonging  to  widely  different  families,  and  which  are  sit¬ 
uated  in  different  parts  of  the  body,  offer,  under  our  pres¬ 
ent  state  of  ignorance,  a  difficulty  almost  exactly  parallel 
with  that  of  the  electric  organs.  Other  similar  cases  could 
be  given;  for  instance  in  plants,  the  very  curious  contriv¬ 
ance  of  a  mass  of  pollen-grains,  borne  on  a  foot-stalk  with 
an  adhesive  gland*  is  apparently  the  same  in  Orchis  and 
Asclepias,  genera  almost  as  remote  as  is  possible  among 
flowering  plants;  but  here  again  the  parts  are  not 
homologous.  In  all  cases  of  beings,  far  removed  from 
each  other  in  the  scale  of  organization,  which  are  fur¬ 
nished  with  similar  and  peculiar  organs,  it  will  be  found 
that  although  the  general  appearance  and  function  of  the 
organs  may  be  the  same,  yet  fundamental  differences 
between  them  can  always  be  detected.  For  instance,  the 
eyes  of  Cephalopods  or  cuttle-fish  and  of  vertebrate  ani¬ 
mals  appear  wonderfully  alike;  and  in  such  widely  sun¬ 
dered  groups  no  part  of  this  resemblance  can  be  due 
to  inheritance  from  a  common  progenitor.  Mr.  Mivart 
has  advanced  this  case  as  one  of  special  difficulty,  but  I 
am  unable  to  see  the  force  of  his  argument.  An  organ 
for  vision  must  be  formed  of  transparent  tissue,  and  must 
include  some  sort  of  lens  for  throwing  an  image  at  the 
back  of  a  darkened  chamber.  Beyond  this  superficial  re¬ 
semblance,  there  is  hardly  any  real  similarity  between  the 
eyes  of  cuttle-fish  and  vertebrates,  as  may  be  seen  by  con¬ 
sulting  IienseAs  admirable  memoir  on  these  organs  in  the 
Cephalopoda.  It  is  impossible  for  me  here  to  enter  on 
details,  but  I  may  specify  a  few  of  the  points  of  difference. 
The  crystalline  lens  in  the  higher  cuttle-fish  consists  of 
two  parts,  placed  one  behind  the  other  like  two  lenses, 
both  having  a  very  different  structure  and  disposition  to 
what  occurs  in  the  vertebrata.  The  retina  is  wholly  dif¬ 
ferent,  with  an  actual  inversion  of  the  elemental  parts, 
and  with  a  large  nervous  ganglion  included  within  the 
membranes  of  the  eye.  The  relations  of  the  muscles 
are  as  different  as  it  is  possible  to  conceive,  and  so  in 
in  other  points.  Hence  it  is  not  a  little  difficult  to  decide 
how  far  even  the  same  terms  ought  to  be  employed  in 
describing  the  eyes  of  the  Cephalopoda  and  Vertebrata. 
It  is,  of  course,  open  to  any  one  to  deny  that  the  eye  in 


OF  NATURAL  SELECTION. 


181 


either  case  could  have  been  developed  through  the  natural 
selection  of  successive  slight  variations;  but  if  this  be  ad¬ 
mitted  in  the  one  case  it  is  clearly  possible  in  the  other; 
and  fundamental  differences  of  structure  in  the  visual 
organs  of  two  groups  might  have  been  anticipated,  in  ac¬ 
cordance  with  this  view  of  their  manner  of  formation. 
As  two  men  have  sometimes  independently  hit  on  the 
same  invention,  so  in  the  several  foregoing  cases  it  appears 
that  natural  selection,  working  for  the  good  of  each  being, 
and  taking  advantage  of  all  favorable  variations,  has  pro¬ 
duced  similar  organs,  as  far  as  function  is  concerned,  in 
distinct  organic  beings,  which  owe  none  of  their  structure 
in  common  to  inheritance  from  a  common  progenitor. 

Fritz  Muller,  in  order  to  test  the  conclusions  arrived  at 
in  this  volume,  has  followed  out  with  much  care  a  nearly 
similar  line  of  argument.  Several  families  of  crustaceans 
include  a  few  species,  possessing  an  air-breathing  appara¬ 
tus  and  fitted  to  live  out  of  the  water.  In  two  of  these 
families,  which  were  more  especially  examined  by  Muller, 
and  which  are  nearly  related  to  each  other,  the  species 
agree  most  closely  in  all  important  characters:  namely  in 
their  sense  organs,  circulating  systems,  in  the  position  of 
the  tufts  of  hair  within  their  complex  stomachs,  and  lastly  in 
the  whole  structure  of  the  water-breathing  branchiae,  even  to 
the  microscopical  hooks  by  which  they  are  cleansed.  Hence 
it  might  have  been  expected  that  in  the  few  species  belong¬ 
ing  to  both  families  which  live  on  the  land,  the  equally 
important  air-breathing  apparatus  would  have  been  the 
same;  for  why  should  this  one  apparatus,  given  for  the 
same  purpose,  have  been  made  to  differ,  while  all  the  other 
important  organs  were  closely  similar,  or  rather,  identical. 

Fritz  Muller  argues  that  this  close  similarity  in  so 
many  points  of  structure  must,  in  accordance  with  the 
views  advanced  by  me,  be  accounted  for  by  inheritance 
from  a  common  progenitor.  But  as  the  vast  majority  of 
the  species  in  the  above  two  families,  as  well  as  most 
other  crustaceans,  are  aquatic  in  their  habits,  it  is  improb¬ 
able  in  the  highest  degree  that  their  common  progenitor 
should  have  been  adapted  for  breathing  air.  Muller 
was  thus  led  carefully  to  examine  the  apparatus  in  the  air- 
breathing  species;  and  he  found  it  to  differ  in  each  in 
several  important  points,  as  in  the  position  of  the  orifices. 


182 


DIFFICULTIES  OF  TIIE  THEORY 


in  the  manner  in  which  they  are  opened  and  closed,  and  in 
some  accessory  details.  Now  such  differences  are  intelligi¬ 
ble,  and  might  even  have  been  expected,  on  the  supposition 
that  species  belonging  to  distinct  families  had  slowly  be¬ 
come  adapted  to  live  more  and  more  out  of  water,  and  to 
breathe  the  air.  For  these  species,  from  belonging  to  dis¬ 
tinct  families,  'would  have  differed  to  a  certain  extent,  and 
in  accordance  with  the  principle  that  the  nature  of  each 
variation  depends  on  two  factors,  viz.,  the  nature  of  the 
organism  and  that  of  the  surrounding  conditions,  their 
variability  assuredly  would  not  have  been  exactly  the  same. 
Consequently  natural  selection  would  have  had  different 
materials  or  variations  to  work  on,  in  order  to  arrive  at  the 
same  functional  result;  and  the  structures  thus  acquired 
would  almost  necessarily  have  differed.  On  the  hypothesis 
of  separate  acts  of  creation  the  whole  case  remains  unintel¬ 
ligible.  This  line  of  argument  seems  to  have  had  great 
weight  in  leading  Fritz  Muller  to  accept  the  views  main¬ 
tained  by  me  in  this  volume. 

Another  distinguished  zoologist,  the  late  Professor  Cla- 
parede,  has  argued  in  the  same  manner,  and  has  arrived  at 
the  same  result.  He  shows  that  there  are  parasitic  mites 
(Acarida^),  belonging  to  distinct  sub-families  and  families, 
which  are  furnishes  with  hair-claspers.  These  organs  must 
have  been  independently  developed,  as  they  could  not  have 
been  inherited  from  a  common  progenitor;  and  in  the 
several  groups  they  are  formed  by  the  modification  of  the 
fore  legs,  of  the  hind  legs,  of  the  maxillae  or  lips,  and 
of  appendages  on  the  under  side  of  the  hind  part  of  the 
body. 

In  the  foregoing  cases,  we  see  the  same  end  gained  and 
the  same  function  performed,  in  beings  not  at  all  or  only 
remotely  allied,  by  organs  in  appearance,  though  not  in 
development,  closely  similar.  On  the  other  hand,  it  is  a 
common  rule  throughout  nature  that  the  same  end  should 
be  gained,  even  sometimes  in  the  case  of  closely  related  be¬ 
ings,  by  the  most  diversified  means.  How  differently  con¬ 
structed  is  the  feathered  wing  of  a  bird  and  the  membrane- 
covered  wing  of  a  bat;  and  still  more  so  the  four  wings  of  a 
butterfly,  the  two  wings  of  a  fly,  and  the  two  wings  with 
the  eiytra  of  a  beetle.  Bivalve  shells  are  made  to  open  and 


OF  NATURAL  SELECTION . 


183 


shut,  out  on  what  a  number  of  patterns  is  the  hinge  con¬ 
structed,  from  the  long  row  of  neatly  interlocking  teeth 
in  a  Nucula  to  the  simple  ligament  of  a  Mussel!  Seeds 
are  disseminated  by  their  minuteness,  by  their  capsule 
being  converted  into  a  light  balloon-like  envelope,  by 
being  embedded  in  pulp  or  flesh,  formed  of  the  most 
diverse  parts,  and  rendered  nutritious,  as  well  as  conspicu¬ 
ously  colored,  go  as  to  attract  and  be  devoured  by  birds, ' 
by  having  hooks  and  grapnels  of  many  kinds  and  serrated 
awns,  so  as  to  adhere  to  the  fur  of  quadrupeds,  and  by 
being  furnished  with  wings  and  plumes,  as  different  in 
shape  as  they  are  elegant  in  structure,  so  as  to  be  wafted 
by  every  breeze.  I  will  give  one  other  instance:  for  this 
subject  of  the  same  end  being  gained  by  the  most  diversi¬ 
fied  means  well  deserves  attention.  Some  authors  main¬ 
tain  that  organic  beings  have  been  formed  in  many  ways 
for  the  sake  of  mere  variety,  almost  like  toys  in  a  shop, 
but.  such  a  view  of  nature  is  incredible.  With  plants 
having  separated  sexes,  and  with  those  in  which,  though 
hermaphrodites,  the  pollen  does  not  spontaneously  fall  on 
the  stigma,  some  aid  is  necessary  for^  their  fertilization. 
With  several  kinds  this  is  effected  by  the  pollen-grains, 
which  are  light  and  incoherent,  being  blown  by  the  wind 
through  mere  chance  on  to  the  stigma;  and  this  is  the  sim¬ 
plest  plan  which  can  well  be  conceived.  An  almost  equally 
simple,  though  very  different  plan  occurs  in  many  plants  in 
which  a  symmetrical  flower  secretes  a  few  drops  of  nectar, 
and  is  consequently  visited  by  insects;  and  these  carry  the 
pollen  from  the  anthers  to  the  stigma. 

From  this  simple  stage  we  may  pass  through  an  inex¬ 
haustible  number  of  contrivances,  all  for  the  same  pur¬ 
pose  and  effected  in  essentially  the  same  manner,  but  en¬ 
tailing  changes .  in  every  part  of  the  flower.  The  nectar 
may  be  stored  in  variously  shaped  receptacles,  with  the 
stamens  and  pistils  modified  in  many  ways,  sometimes 
forming  trap-like  contrivances,  and  sometimes  capable  of 
neatly  adapted  movements  through  irritability  or  elasticity. 
From  such  structures  we  may  advance  till  we  come  to 
such  a  case  of  extraordinary  adaptation  as  that  lately  de¬ 
scribed  by  Dr.  Criiger  in  the  Coryanthes.  This  orchid  has 
part  of  its  labellum  or  lower  lip  hollowed  out  into  a  great 
bucket,  into  which  drops  of  almost  pure  water  continually 


184 


DIFFICULTIES  OF  THE  TIIEORT 


fall  from  two  secreting  horns  which  stand  above  it;  and 
when  the  bucket  is  half-full,  the  water  overflows  by  a  spout 
on  one  side.  The  basal  part  of  the  labellum  stands  over 
the  bucket,  and  is  itself  hollowed  out  into  a  sort  of  cham¬ 
ber  with  two  lateral  entrances;  within  this  chamber  there 
are  curious  fleshy  ridges.  The  most  ingenious  man,  if  he 
had  not  witnessed  what  takes  place,  could  never  have 
imagined  what  purpose  all  these  parts  serve.  But  Dr. 
Criiger  saw  crowds  of  large  humble-bees  visiting  the  gigan¬ 
tic  flowers  of  this  orchid,  not  in  order  to  suck  nectar,  but 
to  gnaw  off  the  ridges  within  the  chamber  above  the  bucket; 
in  doing  this  they  frequently  pushed  each  other  into  the 
bucket,  and  their  wings  being  thus  wetted  they  could  not 
fly  awav,  but  were  compelled  to  crawl  out  through  the 
passage  formed  by  the  spout  or  overflow.  Dr.  Criiger  saw 
a  “  continual  procession  ”  of  bees  thus  crawling  out  of  their 
involuntary  bath.  The  passage  is  narrow,  and  is  roofed  over 
by  the  column,  so  that  a  bee,  in  forcing  its  way  out,  first 
rubs  its  back  against  the  viscid  stigma  and  then  against  the 
viscid  glands  of  the  pollen-masses.  The  pollen-masses  are 
thus  glued  to  the  back  of  the  bee  which  first  happens  to 
crawl  out  through  the  passage  of  a  lately  expanded  flower, 
and  are  thus  carried  away.  Dr.  Criiger  sent  me  a  flower  in 
spirits  of  wine,  with  a  bee  which  he  had  killed  before  it 
had  quite  crawled  out,  with  a  pollen-mass  still  fastened  to 
its  back.  When  the  bee,  thus  provided,  flies  to  another 
flower,  or  to  the  same  flower  a  second  time,  and  is  pushed 
by  its  comrades  into  the  bucket  and  then  crawls  out  by  the 
passage,  the  pollen-mass  necessarily  comes  first  into  con¬ 
tact  with  the  viscid  stigma,  and  adheres  to  it,  and  the 
flower  is  fertilized.  Now  at  last  we  see  the  full  use  of  every 
part  of  the  flower,  of  the  water-secreting  horns  of  the 
bucket  half-full  of  water,  which  prevents  the  bees  from  flying 
away,  and  forces  them  to  crawl  out  through  the  spout,  and 
rub  against  the  properly  placed  viscid  pollen-masses  and 
the  viscid  stigma. 

The  construction  of  the  flower  in  another  closely  allied 
orchid,  namely,  the  Catasetum,  is  widely  different,  though 
serving  the  same  end;  and  is  equally  curious.  Bees  visit 
these  flowers,  like  those  of  the  Coryanthes,  in  order  to  gnaw 
the  labellum;  in  doing  this  they  inevitably  touch  a.  long, 
tapering,  sensitive  projection,  or,  as  I  have  called  it,  the 


OF  NATURAL  SELECTION. 


185 


antenna.  This  antenna,  when  touched,  transmits  a  sensa¬ 
tion  or  vibration  to  a  certain  membrane  which  is  instantly 
ruptured;  this  sets  free  a  spring  by  which  the  pollen-mass 
is  shot  forth,  like  an  arrow,  in  the  right  direction,  and 
adheres  by  its  viscid  extremity  to  the  back  of  the  bee.  The 
pollen-mass  of  the  male  plant  (for  the  sexes  are  separate  in 
this  orchid)  is  thus  carried  to  the  flower  of  the  female 
plant,  where  it  is  brought  into  contact  with  the  stigma, 
which  is  viscid  enough  to  break  certain  elastic  threads, 
and  retain  the  pollen, thus  effecting  fertilization. 

How,  it  may  be  asked,  in  the  foregoing  and  in  innumer¬ 
able  other  instances,  can  we  understand  the  graduated 
scale  of  complexity  and  the  multifarious  means  for  gaining 
the  same  end.  The  answer  no  doubt  is,  as  already  re¬ 
marked,  that  when  two  forms  vary,  which  already  differ 
from  each  other  in  some  slight  degree,  the  variability  will 
not  be  of  the  same  exact  nature,  and  consequently  the 
results  obtained  through  natural  selection  for  the  same 
general  purpose  will  not  be  the  same.  We  should  also  bear 
in  mind  that  every  highly  developed  organism  has  passed 
through  many  changes;  and  that  each  modified  structure 
tends  to  be  inherited,  so  that  each  modification  will  not 
readily  be  quite  lost,  but  may  be  again  and  again  further 
altered.  Hence,  the  structure  of  each  part  of  each  species, 
for  whatever  purpose  it  may  serve,  is  the  sum  of  many 
inherited  changes,  through  which  the  species  has  passed 
during  its  successive  adaptations  to  changed  habits  and 
conditions  of  life. 

Finally  then,  although  in  many  cases  it  is  most  difficult 
even  to  conjecture  by  what  transitions  organs  have  ariived 
at  their  present  state;  yet,  considering  how  small  the  pro¬ 
portion  of  living  and  known  forms  is  to  the  extinct  and 
unknown,  I  have  been  astonished  how  rarely  an  organ  can 
be  named,  toward  which  no  transitional  grade  is  known  to 
lead.  It  certainly  is  true,  that  new  organs  appearing  as  if 
created  for  some  special  purpose  rarely  or  never  appear  in 
any  being;  as  indeed  is  shown  by  that  old,  but  somewhat 
exaggerated,  canon  in  natural  history  of  “  Natura  non  facit 
saltum.”  We  meet  with  this  admission  in  the  writings  of 
almost  every  experienced  naturalist;  or  as  Milne  Edwards 
has  well  expressed  it,  “Nature  is  prodigal  in  variety,  but 
niggard  in  innovation.”  Why,  on  the  theory  of  Creation, 


186 


ORGANS  OF  LITTLE  IMPORTANCE 


should  there  be  so  much  variety  and  so  little  real  novelty? 
Why  should  all  the  parts  and  organs  of  many  independent 
beings,  each  supposed  to  have  been  separately  created  for 
its  own  proper  place  in  nature,  be  so  commonly  linked  to¬ 
gether  by  graduated  steps?  Why  should  not  Nature  take 
a  sudden  leap  from  structure  to  structure?  On  the  theory 
of  natural  selection,  we  can  clearly  understand  why  she 
should  not;  for  natural  selection  acts  only  by  taking  ad¬ 
vantage  of  slight  successive  variations;  she  can  never  take 
a  great  and  sudden  leap,  but  must  advance  by  short  and 
sure,  though  slow  steps. 

ORGAN'S  OF  LITTLE  APPARENT  IMPORTANCE,  AS  AFFECTED 

BY  NATURAL  SELECTION. 

As  natural  selection  acts  by  life  and  death,  by  the  sur¬ 
vival  of  the  fittest,  and  by  the  destruction  of  the  less  well- 
fitted  individuals,  I  have  sometimes  felt  great  difficulty  in 
understanding  the  origin  or  formation  of  parts  of  little 
importance;  almost  as  great,  though  of  a  very  different 
kind,  as  in  the  case  of  the  most  perfect  and  complex 
organs. 

In  the  first  place,  we  are  much  too  ignorant  in  regard 
to  the  whole  economy  of  any  one  organic  being  to  say 
what  slight  modifications  would  be  of  importance  or  not. 
In  a  former  chapter  I  have  given  instances  of  very  trifling 
characters,  such  as  the  down  on  fruit  and  the  color  of  its 
flesh,  the  color  of  the  skin  and  hair  of  quadrupeds,  which, 
from  being  correlated  with  constitutional  differences,  or 
from  determining  the  attacks  of  insects,  might  assuredly 
be  acted  on  by  natural  selection.  The  tail  of  the  giraffe 
looks  like  an  artificially  constructed  fly-flapper;  and  it 
seems  at  first  incredible  that  this  could  have  been  adapted 
for  its  present  purpose  by  successive  slight  modifications, 
each  better  and  better  fitted,  for  so  trifling  an  object  as  to 
drive  away  flies;  yet  we  should  pause  before  being  too 
positive  even  in  this  case,  for  we  know  that  the  distribu¬ 
tion  and  existence  of  cattle  and  other  animals  in  South 
America  absolutely  depend  on  their  power  of  resisting  the 
attacks  of  insects:  so  that  individuals  which  could  by  any 
means  defend  themselves  from  these  small  enemies,  would 
be  able  to  range  into  pew  pastures  and  thus  gain  a  great 


AFFECTED  BY  NATURAL  SELECTION.  1S7 

advantage.  It  is  not  that  the  larger  quadrupeds  are 
actually  destroyed  (except  in  some  rare  cases)  by  flies,  but 
they  are  incessantly  harassed  and  their  strength  reduced, 
so  that  they  are  more  subject  to  disease,  or  not  so  well 
enabled  in  a  coming  dearth  to  search  for  food,  or  to  escape 
from  beasts  of  prey. 

Organs  now  of  trifling  importance  have  probably  in 
some  cases  been  of  high  importance  to  an  early  progenitor, 
and,  after  having  been  slowly  perfected  at  a  former  period, 
have  been  transmitted  to  existing  species  in  nearly  the 
same  state,  although  now  of  very  slight  use;  but  anv 
actually  injurious  deviations  in  their  structure  would  of 
course  have  been  checked  by  natural  selection.  Seeing 
how  important  an  organ  of  locomotion  the  tail  is  in  most 
aquatic  animals,  its  general  presence  and  use  for  many 
purposes  in  so  many  land  animals,  which  in  their  lungs  or 
modified  swim-bladders  betray  their  aquatic  origin,  may 
perhaps  be  thus  accounted  for.  A  well-developed  tail 
having  been  formed  in  an  aquatic  animal,  it  might  subse¬ 
quently  come  to  be  worked  in  for  all  sorts  of  purposes,  as  a 
fly-flapper,  an  organ  of  prehension,  or  as  an  aid  in  turn- 
ing,  as  in  the  case  .of  the  dog,  though  the  aid  in  this  latter 
respect  must  be  slight,  for  the  hare,  with  hardly  any  tail, 
can  double  still  more  quickly. 

In  the  second  place,  we  may  easily  err  in  attributing 
importance  to  characters,  and  in  believing  that  they  have 
been  developed  through  natural  selection.  We  must  by 
no  means  overlook  the  effects  of  the  definite  action  of 
changed  conditions  of  life,  of  so-called  spontaneous  varia¬ 
tions,  which  seem  to  depend  in  a  quite  subordinate 
degree  on  the  nature  of  the  conditions,  of  the  tendency 
to  reversion  to  long-lost  characters,  of  the  complex 
laws  of  growth,  such  as  of  correlation,  comprehension, 
of  the  pressure  of  one  part  on  another,  etc.,  and  finally  of 
sexual  selection,  by  which  characters  of  use  to  one  sex  are 
often  gained  and  then  transmitted  more  or  less  perfectly  to 
the  other  sex,  though  of  no  use  to  the  sex.  But  structures 
thus  indirectly  gained,  although  at  first  of  no  advantage  to 
a  species,  may  subsequently  have  been  taken  advantage  of 
by  its  modified  descendants,  under  new  conditions  of  life 
and  newly  acquired  habits. 

If  green  woodpeckers  alone  had  existed,  and  we  did  not 


188 


ORGANS  OF  LITTLE  IMPORTANCE 


know  that  there  were  many  black  and  pied  kinds,  I  dare 
say  that  we  should  have  thought  that  the  green  color  was  a 
beautiful  adaptation  to  conceal  this  tree-frequenting  bird 
from  its  enemies;  and  consequently  that  it  was  a  character 
of  importance,  and  had  been  acquired  through  natural 
selection;  as  it  is,  the  color  is  probably  in  chief  part  due  to 
sexual  selection.  A  trailing  palm  in  the  Malay  Archipel¬ 
ago  climbs  the  loftiest  trees  by  the  aid  of  exquisitely  con¬ 
structed  hooks  clustered  around,  the  ends  of  the  branches, 
and  this  contrivance,  no  doubt,  is  of  the  highest  service  to 
the  plant;  but  as  we  see  nearly  similar  hooks  on  many 
trees  which  are  not  climbers,  and  which,  as  there  is  reason 
to  believe  from  the  distribution  of  the  thorn-bearing  species 
in  Africa  and  South  America,  serve  as  a  defense  against 
browsing  quadrupeds,  so  the  spikes,  on  the  palm  may  at 
first  have  been  developed  for  this  object,  and  subsequently 
have  been  improved  and  taken  advantage  of  by  the  .plant, 
as  it  underwent  further  modification  and  became  a  climber. 
The  naked  skin  on  the  head  of  a  vulture  is  generally  con¬ 
sidered  as  a  direct  adaptation  for  wallowing  in  putridity; 
and  so  it  may  be,  or  it  may  possibly  be  due  to  the  direct 
action  of  putrid  matter;  but  we  should  be  very  cautious  in 
drawing  any  such  inference,  when  we  'see  that  the  skin  on 
the  head  of  the  clean-feeding  male  turkey  is  likewise 
naked.  The  sutures  in  the  skulls  of  ycung  mammals 
have  been  advanced  as  a  beautiful  adaptation  for  aiding 
parturition,  and  no  doubt  they  facilitate,  or  may  be  indis 
pen  sable  for  this  act:  but  as  sutures  occur  in  the  skulls  of 
young  birds  and  reptiles,  which  have  only  to  escape  from  a 
broken  egg,  we  may  infer  that  this  structure  has  arisen 
from  the  laws  of  growth,  and  has  been  taken  advantage  of 
in  the  parturition  of  the  higher  animals. 

We  are  profoundly  ignorant  of  the  cause  of.  each  slight 
variation  or  individual  difference;  and  we  are  immediately 
made  conscious  of  this  by  reflecting  on  the  differences 
between  the  breeds  of  our  domesticated  animals  in  differ¬ 
ent  countries,  more  especially  in  the  less  civilized  coun¬ 
tries,  where  there  has  been  but  little  methodical  selection. 
Animals  kept  by  savages  in  different  countries  often  have 
to  struggle  for  their  own  subsistence,  and  are  exposed  to  a 
certain  extent  to  natural  selection,  and  individuals  with 
slightly  different  constitutions  would  succeed  best  under 


AFFECTED  BY  NATURAL  SELECTION.  139 

climates.  With  cattle  susceptibility  to  the  attacks 
of  flies  is  correlated  with  color,  as  is  the  liability  to  be  pois¬ 
oned  by  certain  plants;  so  that  even  color  would  be  thus 
subjected  to  the  action  of  natural  selection.  Some  observ¬ 
ers  are  convinced  that  a  damp  climate  affects  the  growth 
of  the  hair,  and.  that  with  the  hair  the  horns  are  corre¬ 
lated.  Mountain  breeds  always  differ  from  lowland 
breeds;  and .  a  mountainous  country  would  probablv 
affect  the  hind  limbs  from  exercising  them  more,  and 
possibly  even  the  form  of  the  pelvis;  and  then  by  the 
law  of  homologous  variation,  the  front  limbs  and  the  head 
would  probably  be  affected.  The  shape,  also,  of  the  pelvis 
might  affect  by  pressure  the  shape  of  certain  parts  of  the 
young  in  the  womb.  The  laborious  breathing  necessary  in 
high  regions  tends,  as  we  have  good  reason  to  believe,  to 
increase  the  size  of  the  chest;  and  again  correlation  would 
come  into  play.  The  effects  of  lessened  exercise,  together 
with  abundant  food,  on  the  whole  organization  is  probably 
still  more  important;  and  this,  as  H.  von  Nathusius  has 
lately  shown  in  his  excellent  Treatise,  is  apparently  one 
chief  cause  of  the  great  modification  which  the  breeds  of 
swine  have  undergone.  But  we  are  far  too  ignorant  to 
speculate  on  the  relative  importance  of  the  several  known 
and  unknown  causes  of  variation;  and  I  have  made  these 
remarks  only  to  show  that,  if  we  are  unable  to  account  for 
the  characteristic  differences  of  our  several  domestic  breeds, 
which  nevertheless  are  generally  admitted  to  have  arisen 
through  ordinary  generation  from  one  or  a  few  parent- 
stocks,  we  ought  not  to  lay  too  much  stress  on  our  ignor¬ 
ance  of  the  precise  cause  of  the  slight  analogous  differences 
between  true  species. 

UTILITARIAN  DOCTRINE,  HOW  FAR  TRUE:  BEAUTY,  HOW 

ACQUIRED. 

The  foregoing  remarks  lead  me  to  say  a  few  words  on 
the  protest  lately  made  by  some  naturalists  against  the 
utilitarian  doctrine  that  every  detail  of  structure  has  been 
produced  for  the  good  of  its  possessor.  They  believe  that 
many  structures  have  been  created  for  the  sake  of  beauty, 
to  delight  man  or  the  Creator  (but  this  latter  point  is  be¬ 
yond  the  scope  of  scientific  discussion),  or  for  the  sake  of 


190  UTILITARIAN  DOCTRINE,  HOW  FAR  TRUE: 

mere  variety,  a  view  already  discussed.  Such  doctrines,  it 
true,  would  be  absolutely  fatal  to  my  theory.  I  fully 
admit  that  many  structures  are  now  of  no  direct  use  to 
their  possessors,  and  may  never  have  been  of  any  use  to 
their  progenitors;  but  this  does  not  prove  that  they  were 
formed  solely  for  beauty  or  variety.  IN  o  doubt  the  definite 
action  of  changed  conditions,  and  the  various  causes  of 
modifications,  lately  specified,  have  all  produced  an  effect, 
probably  a  great  effect,  independently  of  any  advantage 
thus  gained.  But  a  still  more  important  consideration  is 
that  the  chief  part  of  the  organization  of  every  living 
creature  is  due  to  inheritance;  and  consequently,  though 
each  being  assuredly  is  well  fitted  for  its  place  in  nature, 
many  structures  have  now  no  very  close  and  direct  rela¬ 
tion  to  present  habits  of  life.  Thus,  we  can  hardly  believe 
that  the  webbed  feet  of  the  upland  goose,  or  of  the  frigate- 
bird,  are  of  special  use  to  these  birds;  we  can  not  believe 
that  the  similar  bones  in  the  arm  of  the  monkey,  in  the 
fore  leg  of  the  horse,  in  the  wing  of  the  bat,  and  in  the 
flipper  of  the  seal,  are  of  special  use  to  these  animals.  We 
may  safely  attribute  these  structures  to  inheritance.  But 
webbed  feet  no  doubt  were  as  useful  to  the  progenitor  of 
the  upland  goose  and  of  the  frigate-bird,  as  they  now  are 
to  the  most  aquatic  of  living  birds.  So  we  may  believe 
that  the  progenitor  of  the  seal  did  not  possess  a  flipper, 
but  a  foot  with  five  toes  fitted  for  walking  or  grasping;  and 
we  mav  further  venture  to  believe  that  the  several  bones 
in  the  limbs  of  the  monkey,  horse  and  bat,  were  originally 
developed,  on  the  principle  of  utility,  probably  through 
the  reduction  of  more  numerous  bones  in  the  fin  of  some 
ancient  fish-like  progenitor  of  the  whole  class.  It  is 
scarcely  possible  to  decide  how  much  allowance .  ought,  to 
be  made  for  such  causes  of  change,  as  the  definite,  action 
of  external  conditions,  so-called  spontaneous  variations, 
and  the  complex  laws  of  growth;  but  with  these  important 
exceptions,  we  may  conclude  that  the  structure  of  every 
living  creature  either  now  is,  or  was  formerly,  of  some 
direct  or  iudirect  use  to  its  possessor. 

With  respect  to  the  belief  that  organic  beings  have,  been 
created  beautiful  for  the  delight  of  man — a  belief  which  it 
lias  been  pronounced  is  subversive  of  my  whole  theory  — 
I  may  first  remark  that  the  sense  of  beauty  obviously  de- 


BE  A  XJTY \  HOW  ACQ  VIRED .  191 

pends  on  the  nature  of  the  mind,  irrespective  of  any  real 
quality  in  the  admired  object;  and  that  the  idea  of  what 
is  beautiful,  is  not  innate  or  unalterable.  We  see  this,  for 
instance,  in  the  men  of  different  races  admiring  an  en¬ 
tirely  different  standard  of  beauty  in  their  women.  If  beau¬ 
tiful  objects  had  been  created  solely  for  man’s  gratification, 
it  ought  to  be  shown  that  before  man  appeared  there  was 
less  beauty  on  the  face  of  the  earth  than  since  he  came  on 
the  stage.  Were  the  beautiful  volute  and  cone  shells  of 
the  Eocene  epoch,  and  the  gracefully  sculptured  ammonites 
of  the  Secondary  period,  created  that  man  might  ages 
afterward  admire  them  in  his  cabinet?  Few  objects  are 
more  beautiful  than  the  minute  siliceous  cases  of  the 
diatomaceae  :  were  these  created  that  they  might  be  ex¬ 
amined  and  admired  under  the  higher  "powers  of  the 
microscope?  The  beauty  in  this  latter  case,  and  in  many 
others,  is  apparently  wholly  due  to  symmetry  of  growth. 
Flowers  rank  among  the  most  beautiful  productions  of 
nature;  but  they  have  been  rendered  conspicuous  in  con¬ 
trast  with  the  green  leaves,  and  in  consequence  at  the 
same  time  beautiful,  so  that  they  may  be  easily  observed 
by  insects.  I  have  come  to  this  conclusion  from  finding  it 
an  invariable  rule  that  when  a  flower  is  fertilized  by  the 
wind  it  never  has  a  gaily-colored  corolla.  Several  plants 
habitually  produce  two  kinds  of  flowers;  one  kind  open  and 
colored  so  as  to  attract  insects;  the  other  closed,  not- 
colored,  destitute  of  nectar,  and  never  visited  by  insects. 
Hence,  we  may  conclude  that,  if  insects  had  not  been  de¬ 
veloped  on  the  face  of  the  earth,  our  plants  would  not  have 
been  decked  with  beautiful  flowers,  but  would  have  pro¬ 
duced  only  such  poor  flowers  as  we  see  on  our  fir,  oak,  nut 
and  ash  trees,  on  grasses,  spinach,  docks  and  nettles, 
which  are  all  fertilized  through  the  agency  of  the  wind. 
A  similar  line  of  argument  holds  good  with  fruits;  that  a 
ripe  strawberry  or  cherry  is  as  pleasing  to  the  eye  as  to  the 
palate  that  the  gaily-colored  fruit  of  the  spindle-wood 
tree  and  the  scarlet  berries  of  the  holly  are  beautifu.  objects 
—will  be  admitted  by  every  one.  But  this  beauty  serves 
merely  as  a  guide  to  birds  and  beasts,  in  order  that  the 
fruit  may.  be  devoured  and  the  matured  seeds  dissem¬ 
inated.  I  infer  tnat  this  is  the  case  from  having  as  vet 
found  no  exception  to  the  rule  that  seeds  are  always  thus 


192  UTILITARIAN  DOCTRINE ,  ROW  FAR  TRUE: 


disseminated  when  imbedded  within  a  fruit  of  any  kind 
(that  is  within  a  fleshy  or  pulpy  envelope),  if  it  be  colored 
of  any  brilliant  tint,  or  rendered  conspicuous  by  being 
white  or  black. 

On  the  other  hand,  I  willingly  admit  that  a  great 
number  of  male  animals,  as  all  our  most  gorgeous  birds, 
some  fishes,  reptiles,  and  mammals,  and  a  host  of 
magnificently  colored  butterflies,  have  been  rendered 
beautiful  for  beauty's  sake.  But  this  has  been  effected 
through  sexual  selection,  that  is,  by  the  more  beautiful 
males  having  been  continually  preferred  by  the  females, 
and  not  for  the  delight  of  man.  So  it  is  with  the  music  of 
birds.  We  may  infer  from  all  this  that  a  nearly  similar 
taste  for  beautiful  colors  and  for  musical  sounds  runs 
through  a  large  part  of  the  animal  kingdom.  When  the 
female  is  as  beautifully  colored  as  the  male,  which  is  not 
rarely  the  case  with  birds  and  butterflies,  the  cause  ap¬ 
parently  lies  in  the  colors  acquired  through  sexual  selec¬ 
tion  having  been  transmitted  to  both  sexes,  instead  of  to 
the  males  alone.  How  the  sense  of  beauty  in  its  simplest 
form — that  is,  the  reception  of  a  peculiar  kind  of  pleasure 
from  certain  colors,  forms  and  sounds — nvas  first  developed 
in  the  mind  of  man  and  of  the  lower  animals,  is  a  very  ob¬ 
scure  subject.  The  same  sort  of  difficulty  is  presented  if 
we  inquire  how  it  is  that  certain  flavors  and  odors  give 
pleasure,  and  others  displeasure.  Habit  in  all  these  cases 
appears  to  have  come  to  a  certain  extent  into  play;  but 
there  must  be  some  fundamental  cause  in  the  constitution 
of  the  nervous  system  in  each  species. 

Natural  selection  cannot  possibly  produce  any  modifica¬ 
tion  in  a  species  exclusively  for  the  good  of  another 
species,  though  throughout  nature  one  species  inces¬ 
santly  takes  advantage  of  and  profits  by  the  structures  of 
others.  But  natural  selection  can  and  does  often  produce 
structures  for  the  direct  injury  of  other  animals,  as  we 
see  in  the  fang  of  the  adder,  and  in  the  ovipositor  of  the 
ichneumon,  by  which  its  eggs  are  deposited  in  the  living 
bodies  of  other  insects.  If  it  could  be  proved  that  any 
part  of  the  structure  of  any  one  species  had  been  formed 
for  the  exclusive  good  of  another  species,  it  would  anni¬ 
hilate  my  theory,  for  such  could  not  have  been  produced 


BEA  UTY,  HO  W  ACQ  UIRED.  I93 

through  natural  selection.  Although  many  statements 
may  be  found  in  works  on  natural  history  to  this  effect,  I 
cannot  find  even  one  which  seems  to  me  of  any  weight.  It 
is  admitted  that  the  rattlesnake  has  a  poison  fang  for  its 
own  defence  and  for  the  destruction  of  its  prey;  but  some 
authois  suppose  that  at  the  same  time  it  is  furnished  with 
a  rattle  for  its  own  injury,  namely,  to  warn  its  prey.  I 
would  almost  as  soon  believe  that  the  cat  curls  the  end  of 
its  tail  when  preparing  to  spring,  in  order  to  warn  the 
doomed  mouse.  It  is  a  much  more  probable  view  that  the 
rattlesnake  uses  its  rattle,  the  cobra  expands  its  frill  and 
the  puff-adder  swells  while  hissing  so  loudly  and  harshly, 
in  order  to  alarm  the  many  birds  and  beasts  which  are 
known  to  attack  even  the  most  venomous  species.  Snakes 
act  on  the  same  principle  which  makes  the  hen  ruffle  her 
feathers  and  expand  her  wings  when  a  dog  approaches  her 
chickens.  But  I  have  not  space  here  to  enlarge  on  the 
many  ways  by  which  animals  endeavor  to  frighten  away 
their  enemies. 

atural  selection  will  never  produce  in  a  being  any 
structure  more  injurious  than  beneficial  to  that  being,  for 
natural  selection  acts  solely  by  and  for  the  good  of  each. 
No  organ  will  be  formed,  as  Paley  has  remarked,  for  the 
purpose  of  causing  pain  or  for  doing  an  injury  to  its  pos¬ 
sessor.  If  a  fair  balance  be  struck  between  the  good  and 
evil  caused  by  each  part,  each  will  be  found  on  the  whole 
advantageous.  .  After  the  lapse  of  time,  under  changing 
conditions  of  life,  if  any  part  comes  to  be  injurious,  it  will 
be  modified;,  or  if  it  be  not  so,  the  being  will  become  ex¬ 
tinct  as  myriads  have  become  extinct. 

Natural  selection  tends  only  to  make  each  organic  being 
is  perfect  as,  or  slightly  more  perfect  than  the  other  in¬ 
habitants  of  the  same  country  with  which  it  comes  into  com¬ 
petition.  .  And  we  see  that  this  is  the  standard  of  perfec¬ 
tion  attained  under  nature.  The  endemic  productions  of 
New  Zealand,  for  instance,  are  perfect,  one  compared  with 
another;  but  they  are  now  rapidly  yielding  before  the  ad¬ 
vancing  legions  of  plants  and  animals  introduced  from 
Europe.  Natural  selection  will  not  produce  absolute  per¬ 
fection,.  nor  do  we  always  meet,  as  far  as  we  can  judge, 
with  this  high  standard  under  nature.  The  correction  for 
the  aberration  of  light  is  said  by  Muller  not  to  be  perfect 


194  UTILITARIAN  DOCTRINE ,  BOW  EAR  TRUE: 

even  in  that  most  perfect  organ,  the  human  eye.  Helm¬ 
holtz,  whose  judgment  no  one  will  dispute,  after  describ¬ 
ing  in  the  strongest  terms  the  wonderful  powers  of  the 
human  eye,  adds  these  remarkable  words:  *  That  whicn 
we  have  discovered  in  the  way  of  inexactness  and  imper¬ 
fection  in  the  optical  machine  and  in  the  linage  on  the 
retina,  is  as  nothing  in  comparison  with  the  incongruities 
which  we  have  just  come  across  m  the  domain  of  the  sen¬ 
sations.  One  might  say  that  nature  has  taken  delight  1 
accumulating  contradictions  m  order  to  remove  all  founda¬ 
tion  from  the  theory  of  a  pre-existing  harmony  between 
the  external  and  internal  worlds.”  If  our  reason  leads  us 
to  admire  with  enthusiasm  a  multitude  of  inimitable  con¬ 
trivances  in  nature,  this  same  reason  tells  us,  though  we 
may  easily  err  on  both  sides,  that  some  other  contrivances 
are  less  perfect.  Can  we  consider  the  sting  of  the  bee  as 
perfect,  which,  when  used  against  many  kinds  of  enemies, 
can  not  be  withdrawn,  owing  to  the  backward  serratuies, 
and  thus  inevitably  causes  the  death  of  the  insect  by  teai- 

ing  out  its  viscera?  .  .  ,  ,  •  0 

If  we  look  at  the  sting  of  the  bee,  as  having  existed  m  a 

remote  progenitor,  as  a  boring  and  serrated  instrument, 
like  that  in  so  many  members  of  the  same  great  order,  and 
that  it  has  since  been  modified  but  _  not  perfected  for 
its  present  purpose,  with  the  poison  originally  adapted  for 
some  other  object,  such  as  to  produce  galls,  since  inten¬ 
sified,  we  can  perhaps  understand  how  it  is  that  the  use  of 
the  sting  should  so  often  cause  the  insects  own  death:  for 
if  on  the  whole  the  power  of  stinging  be  useful  to  the  social 
community,  it  will  fulfil  all  the  requirements  of  natural 
selection,  though  it  may  cause  the  death  of  some  few  mem¬ 
bers.  If  we  admire  the  truly  wonderful  power  of  scent  by 
which  the  males  of  many  insects  find  their  females,  can  we 
admire  the  production  for  this  single  purpose  of  thousands 
of  drones,  which  are  utterly  useless  to  the  community  ioj 
any  other  purpose,  and  which  are  ultimately  slaughtered  by 
their  industrious  and  sterile  sisters?  ^  It  may  be  difficult 
but  we  ought  to  admire  the  savage  instinctive  hatred  o^  t  le 
queen-bee,  which  urges  her  to  destroy  the  young  queens,  her 
daughters,  as  soon  as  they  are  born,  or  to  perish  herself  m 
the  combat;  for  undoubtedly  this  is  for  the  good  of  the 
community;  and  maternal  love  or  maternal  hatred,  though 


BE  A  UTT, ,  HO  W  ACQ  UIRED. 


195 


the  latter  fortunately  is  most  rare,  is  all  the  same  to  the 
inexorable  principles  of  .natural  selection.  If  we  admire 
the  several  ingenious  contrivances  by  which  orchids  and 
many  other  plants  are  fertilized  through  insect  agency,  can 
we  consider  as  equally  perfect  the  elaboration  of  dense 
clouds  of  pollen  by  our  fir-trees,  so  that  a  few  granules 
may  be  wafted  by  chance  on  to  the  ovules? 

summary:  the  law  of  unity  of  type  and  of  the  con¬ 
ditions  OF  EXISTENCE  EMBRACED  BY  THE  THEORY  OF 
NATURAL  SELECTION. 

We  have  in  this  chapter  discussed  some  of  the  difficulties 
and  objections  which  may  be  urged  against  the  theory. 
Many  of  them  are  serious;  but  I  think  that  in  the  discussion 
light  has  been  thrown  on  several  facts,  which  on  the  belief 
of  independent  acts  of  creation  are  utterly  obsure.  We 
have  seen  that  species  at  any  one  period  are  not  indefinitely 
variable,  and  are  not  linked  together  by  a  multitude  of 
intermediate  gradations,  partly  because  the  process  of 
natural  selection  is  always  very  slow,  and  at  any  one  time 
acts  only  on  a  few  forms;  and  partly  because  the  very  pro¬ 
cess  of  natural  selection  implies  the  continual  supplanting 
and  extinction  of  preceding  and  intermediate  gradations. 
Closely  allied  species,  now  living  on  a  continuous  area, 
must  often  have  been  formed  when  the  area  was  not  con¬ 
tinuous,  and  when  the  conditions  of  life  did  not  insensibty 
graduate  away  from  one  part  to  another.  When  two  vari¬ 
eties  are  formed  in  two  districts  of  a  continuous  area,  an 
intermediate  variety  will  often  be  formed,  fitted  for  an 
intermediate  zone;  but  from  reasons  assigned,  the  inter¬ 
mediate  variety  will  usually  exist  in  lesser  numbers  than 
the  two  forms  which  it  connects;  consequently  the  two 
latter,  during  the  course  of  further  modification,  from  ex¬ 
isting  in  greater  numbers,  will  have  a  great  advantage  over 
the  less  numerous  intermediate  variety,  and  will  thus  gen¬ 
erally  succeed  in  supplanting  and  exterminating  it. 

We  have  seen  in  this  chapter  how  cautious  we  should  be 
in  concluding  that  the  most  different  habits  of  life  could 
not  graduate  into  each  other;  that  a  bat,  for  instance, 
could  not  have  been  formed  by  natural  selection  from  an 
animal  which  at  first  only  glided  through  the  air. 


196 


SUMMARY, 


We  have  seen  that  a  species  under  new  conditions  of  life 
may  change  its  habits;  or  it  may  have  diversified  habits, 
with  some  very  unlike  those  of  its  nearest  congeners. 
Hence  we  can  understand,  bearing  in  mind  that  each  or¬ 
ganic  being  is  trying  to  live  wherever  it  can  live,  how  it 
has  arisen  that  there  are  upland  geese  with  webbed  feet, 
ground  woodpeckers,  diving  thrushes,  and  petrels  with  the 
habits  of  auks. 

Although  the  belief  that  an  organ  so  perfect  as  the  eye 
could  have  been  formed  by  natural  selection,  is  enough  to 
stagger  anyone;  yet  in  the  case  of  any  organ,  if  we  know 
of  a  long  series  of  gradations  in  complexity,  each  good  for 
its  possessor,  then  under  changing  conditions  of  life,  there 
is  no  logical  impossibility  in  the  acquirement  of  any  con¬ 
ceivable  degree  of  perfection  through  natural  selection. 
In  the  cases  in  which  we  know  of  no  intermediate  or  transi¬ 
tional  states,  we  should  be  extremely  cautious  in  concluding 
that  none  can  have  existed,  for  the  metamorphoses  of  many 
organs  show  what  wonderful  changes  in  function  are  at 
least  possible.  For  instance,  a  swim-bladder  has  appar¬ 
ently  been  converted  into  an  air-breathing  lung.  The 
same  organ  having  performed  simultaneously  very  different 
functions,  and  then  having  been  in  part  or  in  whole  special¬ 
ized  for  one  function;  and  two  distinct  organs  having  per¬ 
formed  at  the  same  time  the  same  function,  the  one  having 
been  perfected  while  aided  by  the  other,  must  often  have 
largely  facilitated  transitions. 

We  have  seen  that  in  two  beings  widely  remote  from  each 
other  in  the  natural  scale,  organs  serving  for  the  same  pur¬ 
pose  and  in  external  appearance  closely  similar  may  have 
been  separately  and  independently  formed;  but  when  such 
organs  are  closely  examined,  essential  differences  in  their 
structure  can  almost  always  be  detected;  and  this  naturally 
follows  from  the  principle  of  natural  selection.  On  the 
other  hand,  the  common  rule  throughout  nature  is  infinite 
diversity  of  structure  for  gaining  the  same  end;  and  this 
again  naturally  follows  from  the  same  great  principle. 

In  many  cases  we  are  far  too  ignorant  to  be  enabled  to 
assert  that  a  part  or  organ  is  so  unimportant  for  the  wel¬ 
fare  of  a  species,  that  modifications  in  its  structure  could 
not  have  been  slowly  accumulated  by  means  of  natural 
selection,  In  many  other  cases,  modifications  are  probably 


SUMMARY. 


197 

the  direct  result  of  the  laws  of  variation  or  of  growth,  in¬ 
dependently  of  any  good  having  been  thus  gained.  But 
even  such  structures  have  often,  as  we  may  feel  assured 
been  subsequently  taken  advantage  of,  and  still  further 
modified,  for  the  good  of  species  under  new  conditions  of 
life.  We  may,  also,  believe  that  a  part  formerly  of  high 
importance  has  frequently  been  retained  (as  the  tail  of  an 
aquatic  animal  by  its  terrestrial  descendants),  though  it 
has  become  of  such  small  importance  that  it  could  not,  in 
its  present  state,  have  been  acquired  by  means  of  natural 
selection. 

Natural,  selection  can  produce  nothing  in  one  species  for 
the  exclusive  good  or  injury  of  another;  though  it  may  well 
pioduce  parts,  organs,  and  excretions  highly  useful  or  even 
indispensable,  or  again  highly  injurious  to  another  species, 
but  in  all  cases  at  the  same  time  useful  to  the  jiossessor. 
In  each  well-stocked  country  natural  selection  acts  through 
the  competition  of  the  inhabitants  and  consequently  leads 
to  success  in  the  battle  for  life,  only  in  accordance  with  the 
standard  of  that  particular  country.  Hence  the  inhabi¬ 
tants  of  one  country,  generally  the  smaller  one,  often  yield 
to  the  inhabitants  of  another  and  generally  the  larger 
country.  For  in  the  larger  country  there  will  have  existed 
more  individuals  and  more  diversified  forms,  and  the  com¬ 
petition  will .  have  been  severer,  and  thus  the  standard  of 
perfection  will  have  been  rendered  higher.  Natural  selec¬ 
tion  will  not  necessarily  lead  to  absolute  perfection;  nor 
as  far  as  we  can  judge  by  our  limited  faculties,  can  absolute 
perfection  be  everywhere  predicated. 

On  the  theory  of  natural  selection  we  can  clearly  under- 
stand  thefuH  meaning  of  that  old  canon  in  natural  historv, 

Natura  non.facit  saltum.”  This  canon,  if  we  look  to  the 
present  inhabitants  alone  of  the  world,  is  not  strictly  cor¬ 
rect;  but  if  we  include  all  those  of  past  times,  whether 
known  or  unknown,  it  must  on  this  theory  be  strictly  true. 

It  is  generally  acknowledged  that  all  organic  beings  have 
been  formed  on  two  great  laws— Unity  of  Type,  and  the 
Conditions  of  Existence.  By  unity  of  type  is  meant  that 
fundamental  agreement  in  structure  which  we  see  in 
organic  beings  of  the  same  class,  and  which  is  quite  inde¬ 
pendent  of  their  habits  of  life.  On  my  theory,  unity  of 
type  is  explained  by  unity  of  descent.  The  expression  of 


193 


SUMMARY . 


conditions  of  existence,  so  often  insisted  on  by  the  illus¬ 
trious  Cuvier,  is  fully  embraced  by  the  principle  of  natural 
selection.  For  natural  selection  acts  by  either  now  adapt¬ 
ing  the  varying  parts  of  each  being  to  its  organic  and  in¬ 
organic  conditions  of  life;  or  by  having  adapted  them 
during  past  periods  of  time:  the  adaptations  being  aided  in 
many  cases  by  the  increased  use  or  disuse  of  parts,  being 
affected  by  the  direct  action  of  the  external  conditions  of 
life,  and  subjected  in  all  cases  to  the  several  laws  of  growth 
and  variation.  Hence,  in  fact,  the  law  of  the  Conditions 
of  Existence  is  the  higher  law;  as  it  includes,  through  the 
inheritance  of  former  variations  and  adaptations,  that  of 
Unity  of  Type. 


f 


MISCELLANEOUS  OBJECTIONS . 


199 


CHAPTER  VII. 

MISCELLANEOUS  OBJECTIONS  TO  THE  THEORY  OF  NATURAL 

SELECTION. 

Longevity  —  Modifications  not  necessarily  simultaneous  —  Modifica¬ 
tions  apparently  of  no  direct  service  —  Progressive  develop¬ 
ment  Characters  of  small  functional  importance,  the  most  con¬ 
stant — .Supposed  incompetence  of  natural  selection  to  account  for 
the  incipient  stages  of  useful  structures — Causes  which  interfere 
with  the  acquisition  through  natural  selection  of  useful  struct¬ 
ures — Gradations  of  structure  with  changed  functions — Widely 
different  organs  in  members  of  the  same  class,  developed  from 
one  and  the  same  source — Reasons  for  disbelieving  in  great  and 
abrupt  modifications. 

I  will  devote  this  chapter  to  the  consideration  of 
various  miscellaneous  objections  which  have  been  advanced 
against  my  views,  as  some  of  the  previous  discussions  may 
thus  be  made  clearer;  but  it  would  be  useless  to  discuss  all 
of  them,  as  many  have  been  made  by  writers  who  have  not 
taken  the  trouble  to  understand  the"  subject.  Thus  a  dis- 
guished  German  naturalist  has  asserted  that  the  weakest 
part  of  my  theory  is,  that  I  consider  all  organic  beings  as 
imperfect:  what  I  have  really  said  is,  that  all  are  not  as 
perfect  as  they  might  have  been  in  relation  to  their  condi¬ 
tions;  and  this  is  shown  to  be  the  case  by  so  many  native 
forms  in  many  quarters  of  the  world  having  yielded  their 
places  to  intruding  foreigners.  Nor  can  organic  beings, 
even  if  they  were  at  any  one  time  perfectly  adapted  to 
their  conditions  of  life,  have  remained  so,  when  their  con¬ 
ditions  changed,  unless  they  themselves  likewise  changed; 
and  no  one  will  dispute  that  the  physical  conditions  of 
each  country,  as  well  as  the  number  and  kinds  of  its  inhab¬ 
itants,  have  undergone  many  mutations. 

A  critic  has  lately  insisted,  with  some  parade  of  mathe¬ 
matical  accuracy,  that  longevity  is  a  great  advantage  to  all 
species,  so  that  he  who  believes  in  natural  selection  ‘‘must 


200  MISCELLANEOUS  OBJECTIONS  TO  TEE 

arrange  his  genealogical  tree  in  such  a  manner  that  all 
the  descendants  have  longer  lives  than  their  progenitors! 
Cannot  our  critics  conceive  that  a  biennial  plant  or  one  of 
the  lower  animals  might  range  into  a  cold  climate  and 
perish  there  every  winter;  and  yet,  owing  to  advantages 
gained  through  natural  selection,  survive  from  year  to 
year  by  means  of  its  seeds  or  ova?  Mr.  E.  Ray  Lankester 
has  recently  discussed  this  subject,  and  he  concludes,  as 
far  as  its  extreme  complexity  allows  him  to  form  a  judg¬ 
ment,  that  longevity  is  generally  related  to  the  standard  of 
each  species  in  the  scale  of  organization,  as  well  as  to  the 
amount  of  expenditure  in  reproduction  and  in  geneial 
activity.  And  these  conditions  have,  it  is  probable,  been 
largely  determined  through  natural  selection. 

It  has  been  argued  that,  as  none  of  the  animals  and 
plants  of  Egypt,  of  which  we  know  anything,  have  changed 
during  the  last  three  or  four  thousand  years,  so  probably 
have  none  in  any  part  of  the  world.  But,  as  Mr.  G.  H. 
Lewes  has  remarked,  this  line  of  argument  proves  too 
much,  for  the  ancient  domestic  races  figured  on  the 
Egyptian  monuments,  or  embalmed,  are  closely  similar  or 
even  identical  with  those  now  living;  yet  all  naturalists 
admit  that  such  races  have  been  produced  through  the 
modification  of  their  original  types.  The  many  animals 
which  have  remained  unchanged  since  the  commencement 
of  the  glacial  period,  would  have  been  an  incomparably 
stronger  case,  for  these  have  been  exposed  to  great  changes 
of  climate  and  have  migrated  over  great  distances;  whereas, 
in  Egypt,  during  the  last  several  thousand  years,  the  con¬ 
ditions  of  life,  as  far  as  we  know,  have  remained  absolutely 
uniform.  The  fact  of  little  or  no  modification  having 
been  effected  since  the  glacial  period,  would  have  been  of 
some  avail  against  those  who  believe  in  an  innate  and 
necessary  law  of  development,  but  is  powerless  against  the 
doctrine  of  natural  selection  or  the  survival  of  the  fittest, 
which  implies  that  when  variations  or  individual  differences 
of  a  beneficial  nature  happen  to  arise,  these  will  be  pre¬ 
served;  but  this  will  be  effected  only  under  certain  favor¬ 
able  circumstances.  . 

The  celebrated  palaeontologist,  Bronn,  at  the  close  of  his 
German  translation  of  this  work,  asks  how,  on  the  prin¬ 
ciple  of  natural  selection,  can  a  variety  live  side  by  side 


THEORY  OE  NATURAL  SELECTION.  201 

wUh  the  pareut;  species?  If  both  have  become  fitted  for 
?ive  different  habits  of  life  or  conditions,  they  might 
live  >gether;_  and  if  we  lay  on  one  side  polymorohic 

nature’  an/all  nm  6  Vtariabilit3'  seems  to  be  of  a  peculiar 
aIbinisn  fdfo  f)  i  'e  temPorary  variations,  such  as  size, 
aioimsm,  etc.,  the  more  permanent  varieties  are  generally 

uch  ksaSWhaSls  T  diS,C0Ve^  inbabiting  distinction  ! 

Moreover  fn  the  1“'  l0/  ***,  *?  or  moist  districts! 
oi cover,  in  the  case  of  animals  which  wander  much 

about  and  cross  freely,  their  varieties  seem  to  be  generally 
confined  to  distinct  regions.  fceneiaiiy 

Broun  also  insists  _  that  distinct  species  never  differ 
om  each  other  in  single  characters,  but  in  many  parts- 
and  he  asks,  how  it  always  comes  that  many  pai  t/of  the’ 

SnT  •  S,b°U  d  bave  been  modified  at  the  same  time 
th lough  variation  and  natural  selection?  But  there  is  no 

necessity  for  supposing  that  all  the  parts  of  any  being 
have  been  simultaneously  modified.  The  most  striking 
modifications,  excellently  adapted  for  some  purpose  might5 

a  ioZ  ifXhf  7T:ked’  be  ac<3uired  byPsueSve  4,  : 

ations,  if  slight,  first  m  one  part  and  then  in  another-  and 

pear  to  us“as  i?  tb™  FH*?  M  -to«etbel'’  tbeJ  would  ap 
Tut  hit  f  i.they  had  been  simultaneously  developed. 
The  best  answer,  however,  to  the  above  objection  is  afforded 
by  those  domestic  races  which  have  been  modified  chiefly 
tlnough  man  s  power  of  selection,  for  some  special  purpose^ 

mastiff  ‘tV -Ce  1“  1  d!'ay-h01se>  at  «ie  |reyhouncf  and 
mastiff  Their  whole  frames,  and  even  their  mental  char¬ 
acteristics,  have  been  modified;  but  if  we  could  trace  each 
step  in  the  history  of  their  transformation — and  the  latter 
steps  can  be  traced— we  should  not  see  great  and  simulta- 

mo°dUifiSan^  bUt  filIt  0IlePart  and  then  another  slightly 
modified  and  improved.  Even  when  selection  has  been 

plied  by  man  to  some  one  character  alone — of  which  our 

be  found1  th^lth**  ‘wu-8*  instan°es— it  will  invariably 

flower  fdn,ff  L  lih0Ughi  “t  one  Part>  whetlmr  it  be  the 
nower,  fruit,  or  leaves,  has  been  greatly  changed  almost 

hi  ^  -w6r iparts illave  been  sightly  modified.  ^  This  may 
be  attributed  partly  to  the  principle  of  correlated  growth 
and  partly  to  so-called  spontaneous  variation.  S  ’ 

A  much  more  serious  objection  has  been  urged  by  Broun 
and  recently  by  Broca,  namely,  that  maSy  characters 


202  MISCELLANEOUS  OBJECTIONS  TO  THE 

appear  to  be  of  no  service  whatever  to  their  possessors,  and 
therefore  cannot  have  been  influenced  through  natural 
selection.  Bronn  adduces  the  length  of  the  ears  and  taiio 
in  the  different  species  of  hares  and  mice— the  complex 
folds  of  enamel  in  the  teeth  of  many  animals,  and  a  multi¬ 
tude  of  analogous  cases.  With  respect  to  plants,  this  sub¬ 
ject  has  been  discussed  by  Nageli  m  an  admirable  essay. 
He  admits  that  natural  selection  has  effected  much,  but  he 
insists  that  the  families  of  plants  differ  chiefly  from  each 
other  in  morphological  characters,  which  appear  to  be  quite 
unimportant  for  the  welfare  of  the  species.  He  conse¬ 
quently  believes  in  an  innate  tendency  toward  pi  ogiessive 
and  more  perfect  development.  He  specifies  the  arrange¬ 
ment  of  the  cells  in  the  tissues,  and  of  the  leaves  on  the 
axis,  as  cases  in  which  natural  selection  could  not  have 
acted.  To  these  may  be  added  the  numerical  divisions  m 
the  parts  of  the  flower,  the  position  of  the  ovules,  the 
shape  of  the  seed,  when  not  of  any  use  for  dissemina- 

10There’is  much  force  in  the  above  objection.  Neverthe¬ 
less  we  ought,  in  the  first  place,  to  be  extremely  cautious 
in  pretending  to  decide  what  structures  now  are,  or  have 
formerly  been,  of  use  to  each  species.  In  the  second  place, 
it  should  always  be  borne  in  mind  that  when  one  part  is 
modified,  so  will  be  other  parts,  through  certain  dimly  seen 
causes,  such  as  an  increased  or  diminished  flow  of  nutri¬ 
ment  to  a  part,  mutual  pressure,  an  early  developed  part 
affecting  one  subsequently  developed,  and  so  forth  as  yell 
as  through  other  causes  which  lead  to  the  many  mysterious 
cases  of  correlation,  which  we  do  not  m  the  least  undei- 
stand.  These  agencies  may  be  all  grouped  together, 
for  the  sake  of  brevity,  under .  the  expression  of 
the  laws  of  growth.  In  the  third  place,  we  have 
to  allow  for  the  direct  and  definite  action  of 

changed  conditions  of  life,  and  for  so-called  spontaneous 
variations,  in  which  the  nature  of  the  conditions  appar¬ 
ently  plays  a  quite  subordinate  part.  Bud-variations,  such 
as  the  appearance  of  a  moss-rose  on  a  common  rose,  01  o 
a  nectarine  on  a  peach-tree,  offer  good  instances  of  spon¬ 
taneous  variations;  but  even  in  these  cases,  if  we  bear  m 
mind  the  power  of  a  minute  drop  of  poison  in  producing 
complex  galls,  we  ought  not  to  feel  too  sure  that  the  above 


THEOR T  OF  NATURAL  SEL E0T10 N.  203 

\ai  iations  aie  not  the  effect  of  some  local  change  in  the 
nature  of  the  sap,  due  to  some  change  in  the  conditions. 
I. here  must  be  some  efficient  cause  for  each  slight  indi¬ 
vidual  difference,  as  well  as  for  more  strongly  marked 
variations  which  occasionally  arise;  and  if  the  unknown 
cause  were  to  act  persistently,  it  is  almost  certain  that  all 
the  individuals  of  the  species  would  be  similarly  modified. 

In  the  earlier  editions  of  this  work  I  underrated,  as  it 

n°'^--Geer^S  frequency  and  importance  of 

modifications  due  to  spontaneous  variability.  But  it  is  im¬ 
possible  to  attribute  to  this  cause  the  innumerable  struct- 
u res. which  are  so  well  adapted  to  the  habits  of  life  of  each 
species.  I  can  no  more  believe  in  this  than  that  the  well- 
adapted  form  of  a  race-horse  or  greyhound,  which  before 
the  principle  of  selection  by  man  was  well  understood,  ex¬ 
cited  so  much  surprise  in  the  minds  of  the  older  natural¬ 
ists,  can  thus  be  explained. 

It  may  be  worth  while  to  illustrate  some  of  the  foregoing 
remarks.  With  respect  to  the  assumed  inutility  of  various 
parts  and  organs,  it  is  hardly  necessary  to  observe  that 
even  m.the  higher  and  best-known  animals  many  struct- 
ures  exist,  which  are  so  highly  developed  that  *  no  one 
doubts  that  they  are  of  importance,  yet  their  use  has  not 
been,  or  has  only  recently  been,  ascertained.  As  Bronn 
gives,  the  length  of  the  ears  and  tail  in  the  several  species 
o  mice  as  instances,  though  trifling  ones,  of  differences  in 
s  tincture  which  can  be  of  no  special  use,  I  may  mention 
that,  according  to  Dr.  Schobl,  the  external  ears  of  the 
common  mouse  are  supplied  in  an  extraordinary  manner 
with  nerves,  so  that  they  no  doubt  serve  as  tactile  organs- 
hence  the  length  of  the  ears  can  hardly  be  quite  unimpor- 
tant.  We  shall,  also,  presently  see  that  the  tail  is  a  highly 
useful  prehensile  organ  to  some  of  the  species;  and  its° use 
would  be  much  influenced  by  its  length. 

With  respect  to  plants,  to  which  on  account  of  Nao'elks 
essay  I  shall  confine  myself  in  the  following  remarks,  it 
will  be  admitted  that  the  flowers  of  the  orchids  present  a 
multitude  of  curious  structures,  which  a  few  years  ago 
would  have  been  considered  as  mere  morphological  differ¬ 
ences  without  any  special  function;  but  they  are  now 
known  to  be  of  the  highest  importance  for  the  fertilization 
of  the  species  through  the  aid  of  insects,  and  have  prob- 


204  MISCELLANEOUS  OBJECTIONS  TO  THE 

ably  been  gained  through  natural  selection.  No  one  until 
lately  would  have  imagined  that  in  dimorphic  and  tri- 
morphic  plants  the  different  lengths  of  the  stamens  and 
pistils,  and  their  arrangement,  could  have  been  of  any 
service,  but  now  we  know  this  to  be  the  case. 

In  certain  whole  groups  of  plants  the  ovules  stand  erect, 
and  in  others  they  are  suspended;  and  within  the  same 
ovarium  of  some  few  plants,  one  ovule  holds  the  former 
and  a  second  ovule  the  latter  position.  These  positions 
seem  at  first  purely  morphological,  or  of  no  physiological 
signification;  but  Dr.  Hooker  informs  me  that  within  the 
same  ovarium,  the  upper  ovules  alone  in  some  cases,  and 
in  others  the  lower  ones  alone  are  fertilized;  and  he  sug¬ 
gests  that  this  probably  depends  on  the  direction  in  which 
the  pollen-tubes  enter  the  ovarium.  If  so,  the  position  of 
the  ovules,  even  when  one  is  erect  and  the  other  suspended 
within  the  same  ovarium,  would  follow  the  selection  of  any 
slight  deviations  in  position  which  favored  their  fertiliza¬ 
tion,  and  the  production  of  seed. 

Several  plants  belonging  to  distinct  orders  habitually 
produce  flowers  of  two  kinds— the  one  open,  of  the  ordi¬ 
nary  structure,  the  other  closed  and  imperfect.  These  two 
kinds  of  flowers  sometimes  differ  wonderfully  in  structure, 
yet  may  be  seen  to  graduate  into  each  other  on  the  same 
plant.  The  ordinary  and  open  flowers  can  be  intercrossed; 
and  the  benefits  which  certainly  are  derived  from  this  pro¬ 
cess  are  thus  secured.  The  closed  and  imperfect  flowers 
are,  however,  manifestly  of  high  importance,  as.  they  yield 
with  the  utmost  safety  a  large  stock  of  seed,  with  the  ex¬ 
penditure  of  wonderfully  little  pollen.  The  two  kinds  of 
flowers  often  differ  much,  as  just  stated,  in  structure..  The 
petals  in  the  imperfect  flowers  almost  always  consist  of 
mere  rudiments,  and  the  pollen-grains  are  reduced  in 
diameter.  In  Ononis  columnse  five  of  the  alternate  sta¬ 
mens  are  rudimentary;  and  in  some  species  of  Viola  three 
stamens  are  in  this  state,  two  retaining  their  proper  func¬ 
tion,  but  being  of  very  small  size.  In  six  out  of  thirty  of 
the  closed  flowers  in  an  Indian  violet  (name  unknown,  for 
the  plants  have  never  produced  with  me  perfect  flowers), 
the  sepals  are  reduced  from  the  normal  number  of  five  to 
three.  In  one  section  of  the  Malpighiaceae  the  closed 
flowers,  according  to  A.  de  Jussieu,  are  still  further  modi- 


THEORY  OF  NATURAL  SELECTION  ^05 

fled,  for  the  five  stamens  which  stand  opposite  to  the  sepals 
me  all  aborted,  a  sixth  stamen  standing  opposite  to  a  petal 
being  alone  developed;  and  this  stamen  fnot  present  in 
th®  ordinal y  flowers  of  this  species;  the  style  is  aborted- 
and  the  ovana  are  reduced  from  three  to  two.  Now  al¬ 
though  natural  selection  may  well  have  had  the  power  to 
prevent  some  of  the  flowers  from  expanding,  and  to  reduce 
tie  amount  of  pollen,  when  rendered  by  the  closure  of  the 
floweis  superfluous,  yet  hardly  any  of  the  above  special 

„can  have  been  thus  determined,  but  must 
have  followed  from  the  laws  of  growth,  including  thefunc- 

t  on  of  ?betlVny  °f  PurtiS’  dVnng  the  Progress  of  the  reduc¬ 
tion  of  the  pollen  and  the  closure  of  the  flowers. 

fT,_ ,*s  so  "ecessary  to  appreciate  the  important  effects  of 
the  laws  of  growth,  that  I  will  give  some  additional  cases 
of  another  kind,  namely  of  differences  in  the  same  part  or 

plain?'  dTn  ti  dl*ereno,es  \n  relative  position  on  the  same 
plant.  In  the  Spanish  chestnut,  and  in  certain  fir-trees, 

SeW$eS-0f  d'vergencf  of  the  leaves  differ,  according  to 
Schacht,  m  the  nearly  horizontal  and  in  the  upnght 
branches.  In  the  common  rue  and  some  other  plants,  one 
flowei,  usually  the  central  or  terminal  one,  opens  first,  and 

P?ta  s’  and  five  divisions  to  the  ovarium; 
In  tl?  \e5  flo'rers  on  the  plant  are  tetramerous. 

in  the  Biitigh  Adoxa  the  uppermost  flower  generally  has 
two  calyx-lobes  with  the  other  organs  tetramerous,  while 
«  e  surroundmg  flowers  generally  have  three  calyx-lobes 

m  l  TT^m,  i  f  °rfn!,  Pentamerous.  In  many  Composite 
and  Umbelliferaj  (and  in  some  other  plants)  the  circum- 

eiential  flowers  have  their  corollas  much  more  developed 

with  th  °Seh°Vhe  C?n?er;  and  this  seems  often  connected 
abortiou  of  the  reproductive  organs.  It  is  a  more 

‘  Previously  referred  to,  that  the  achenes 

,i  •  ,tle  circumference  and  center  sometimes  differ 
greatly  in  form,  color  and  other  characters.  In  Cartha- 
mus  and  some  other  Composite  the  central  achenes  alone 
are  furnished  with  a  pappus;  and  in  Hvoseris  the  same 
ITmhJrf  dS  a°benes  of  three  different  forms.  In  certain 

ortW  iferai  t  le  eiXt,f10r  seeds>  according  to  Tausch,  are 
rthospermous,  and  tho  central  one  ccelospermous,  and  this 

is  a  character  which  was  considered  by  De  Candolle  to  be  in 
othei  species  of  the  highest  systematic  importance.  Pro- 


206 


miscellaneous  objections  to  the 


fessor  Braun  mentions  a  Fumariaceous  genus,  in  which  the 

flowers  in  the  lower  part  of  the  spike  bear  oval  ribbed 

one-seeded  nutlets;  and  in  the  upper  part  of  the  SP‘“> 

lanceolate,  two-valved  and  two-seeded  sihques 

several  eases,  with  the  exception  o  ,  .  ,  i  flowers 

„nprj  rav  florets  which  are  of  service  m  making  tiie  noweis 

conspicuous  to ’insects,  natural  seiection  cannot  as  fa^as 

we  can  iudge,  have  come  into  play,  or  only  m  a  quite  suo 
onlinate  manner.  All  these  modifications  follow  from  the 
relative  position  and  inter-action  of  the  parts;  and  it  can 
hardly  be  doubted  that  if  all  the  flowers  and  leaves  on  the 
same  "plant  had  been  subjected  to  the  same  external  and 
internal  'condition,  as  are  hie  flowers  and  e-es  in  cer  am 
positions,  all  would  have  been  modified  in  the 

"numerous  other  cases  we  find  modifications  of  struct¬ 
ure,  which  are  considered  by  botanists  to  be  generally  of  a 
highly  important  nature,  affecting  only  some  of  the  flowers 
orf  the  same  plant,  or  occurring  on  distinct  plants,  which 
otow  close  together  under  the  same  conditions.  As  these 
variation? seem  of  no  special  use  to  the  plants  they  canno 
have  been  influenced  by  natural  se lection  Of  the a  ca 
we  are  quite  ignorant;  we  cannot  even  attnbute  them,  as 
in  the  last  clasf  of  cases,  to  any  proximate  agency,  such  as 
relative  position.  I  will  give  only  a  few  instances  It  is 
so  common  to  observe  on  the  same  plant  flowers  ndiflm 
pntlv  tetramerous,  nentamerous,  etc.,  that  I  need  not  g 

Numerical  variation.  are  ““HSS 
rare  when  the  parts  are  few,  I  may  mention  that,  accoia 
ing  to  De  Candolle,  the  flowers  of  Papaver  bracteatum- 
offer  either  two  sepals  with  four  petals  (which  is 
common  type  with  poppies) ,  or  three  sepals  with  s  x 
netals.  The  manner  in  which  the  petals  are  folded  1 
bud  is  in  most  groups  a  very  constant  morphological  c  - 
acter*  but  Professor  Asa  Gray  states  that  with  some  specie 
of  Mimulus,  the  sestivation  is  almost  as  frequently  that ;  of 
the  Rhinanthidese  as  of  the  Antirrhimdeae,  to  which .latte 
tribe  the  genus  belongs.  Aug.  St.  Hilaire  gi\es  t  _ 
lowing  case®  :  the  genus  Zanthoxylon  belongs  to  a  division 
of  the  Rutace*  with  a  single  ovary,  but  m  some  spe 
flowers  may  be  found  on  (the  same  plant,  and  even  in  t 
same  panicle,  with  either  one  or  two  ovaries.  In 


THEOR  Y  OF  NA  TURAL  SELEOTIO. N.  207 

Ilelianthemum  the  capsule  has  been  described  as  unilocu¬ 
lar  or  tri-locular;  and  in  H.  mutabile,  “Une  lame  plus  on 
moms  large,  s  etend  entre  le  pericarpe  et  le  placenta/'  In 
the  flowers  of  Saponaria  officinalis  Dr.  Masters  has 
observed  instances  of  both  marginal  and  free  central  plac- 
entation.  Lastly,  St.  Hilaire  found  toward  the  southern 
extreme  of  the  range  of  Gomphia  oleseformis  two  forms 
which  he  did  not  at  first  doubt  were  distinct  species,  but 
he  subsequently  saw  them  growing  on  the  same  bush:  and 
he  then  adds,  “  Voila  done  dans  un  meme  individu  des 
loges  et  un  style  qui  se  rattachent  tantot  a  un  axe  verticale 
et  tantot  a  un  gynobase/' 

We  thus  see  that  with  plants  many  morphological 
changes  may  be  attributed  to  the  laws  of  growth  and  the 
mtei -action  of  parts,  independently  of  natural  selection. 
But  with  respect  to  Nageli's  doctrine  of  an  innate  tend¬ 
ency  tovvard  perfection  or  progressive  development,  can  it 

f-u  wi  m  i  e  case  ^iese  strongly  pronounced  variations, 
that  the  plants  have  been  caught  in  the  act  of  progressing 
toward  a  higher  state  of  development?  On  the  contrary* 
j-S10?  ^  m?er  -from  the  mere  fact  of  the  parts  in  question 
drftering  °r  varying  greatly  on  the  same  plant,  that  such 
modifications  were  of  extremely  small  importance  to  the 
plants  themselves,  of  whatever  importance  they  may  gener¬ 
ally  be  to  us  for  our  classifications.  The  acquisition  of  a 
useless  part  can  hardly  be  said  to  raise  an  organism  in  the 
natuial  scale;  and  in  the  case  of  the  imperfect,  closed 
flowers  above  described,  if  any  new  principle  has  to  be 
invoked,  it  must  be  one  of  retrogression  rather  than  of 
pi  ogi  ession;  and  so  it  must  be  with  many  parasitic  and 
degraded  animals..  We  are  ignorant  of  the'exciting  cause 
of  the  above  specified  modifications;  but  if  the  unknown 
cause  were  to  act  almost  uniformly  for  a  length  of  time 
)'e  niay  infer  that  the. result  would  be  almost  uniform;  and 

ln  i.]is  -,c?'se  ,a^  ^ie  individuals  of  the  species  would  be 
modified  in  the  same  manner. 

From  the  fact  of  the  above  characters  being  unimpor- 
tant  for  the  welfare  of  the  species,  any  slight  variations 
which  occurred  m  them  would  not  have  been  accumulated 
and  augmented  through  natural  selection.  A  structure 
which  has  been  developed  through  long-continued  selec- 
1011,  when  it  ceases  to  be  of  service  to  a  species,  generally 


208  MISCELLANEOUS  OBJECTIONS  TO  TEE! 

becomes  variable,  as  we  see  with  rudimentary  organs;  for 
it  will  no  longer  be  regulated  by  this  same  power  of  selec¬ 
tion.  But  when,  from  the  nature  of  the  organism  and  of 
the  conditions,  modifications  have  been  induced  which  are 
unimportant  for  the  welfare  of  the  species,  they  may  be, 
and  apparently  often  have  been,  transmitted  in  nearly  the 
same  state  to  numerous,  otherwise  modified,  descendants. 
It  cannot  have  been  of  much  importance  to  thegieatei 
number  of  mammals,  birds,  or  reptiles,  whether  they  were 
clothed  with  hair,  feathers  or  scales;  yet  hair  has  been  trans¬ 
mitted  to  almost  all  mammals,  feathers  to  all  birds,  and 
•scales  to  all  true  reptiles.  A  structure,  whatever  it  may 
be,  which  is  common  to  many  allied  forms,  is  ranked  by 
us' as  of  high  systematic  importance,  and  consequently  is 
often  assumed  to  be  of  high  vital  importance  to  the 
species.  Thus,  as  I  am  inclined  to  believe,  morphological 
differences,  which  we  consider  as  important— such  as  the 
arrangement  of  the  leaves,  the  divisions  of  the  flowei  01  of 
the  ovarium,  the  position  of  the  ovules,  etc.,  first  appeared 
in  many  cases  as  fluctuating  variations,  which  sooner.  01 
later  became  constant  through  . the  nature  of  the  organism 
and  of  the  surrounding  conditions,  as  well  as  through  the 
intercrossing  of  distinct  individuals,  but  not  through 
natural  selection;  for  as  these  morphological  characters  do 
not  affect  the  welfare  of  the  species,  any  slight  deviations  in 
them  could  not  have  been  governed  or  accumulated  through 
this  latter  agency.  It  is  a  strange  result  which  we  thus 
arrive  at, namely,  that  characters  of  slight  vital  importance  to 
the  species,  are  the  most  important  to  the  systematist,  but, 
as  we  shall  hereafter  see  when  we  treat  of  the  genetic 
principle  of  classification,  this  is  by  no  means  so  paradoxi¬ 
cal  as  it  may  at  first  appear. 

Although  we  have  no  good  evidence  of  the  existence 
in  organic  beings  of  an  innate,  tendency  toward  progressive 
development,  yet  this  necessarily  follows,  as  I  have  attempt¬ 
ed  to  show  in  the  fourth  chapter,  through  the  continued 
action  of  natural  selection.  For  the  best  definition  which 
has  ever  been  given  of  a  high  standard  of  organization,  is 
the  degree  to  which  the  parts  have  been  specialized  or  dif¬ 
ferentiated;  and  natural  selection  tends  toward,  this  end, 
inasmuch  as  the  parts  are  thus  enabled  to  perform  theii 
functions  more  efficiently. 


209 


THEORY  OF  NATURAL  SELECTION. 

A  distinguished  zoologist,  Mr.  St.  George  Mivart,  has 
recently  collected  all  the  objections  which  have  ever  been 
advanced  by  myself  and  others  against  the  theory  of  natural 
selection,  as  propounded  by  Mr.  Wallace  and  myself,  and 
has  illustrated  them  with  admirable  art  and  force.  When 
thus  marshaled,  they  make  a  formidable  array;  and  as  it 
forms  no  part  of  Mr.  MivarGs  plan  to  give  the  various 
facts  and  considerations  opposed  to  his  conclusions,  no 
slight  effort  of  reason  and  memory  is  left  to  the  reader, 
who  may  wish  to  weigh  the  evidence  on  both  sides.  When 
discussing  special  cases,  Mr.  Mivart  passes  over  the  effects 
of  the  increased  use  and  disuse  of  parts,  which  I  have 
always  maintained  to  be  highly  important,  and  have  treated 
in  my  “  Variation  under  Domestication  ”  at  greater  length 
than,  as  I  believe,  any  other  writer.  He  likewise  often 
assumes  that  I  attribute  nothing  to  variation,  independently 
of  natural  selection,  whereas  in  the  work  just  referred  to 
I  have  collected  a  greater  number  of  well-established  cases 
than  can  be  found  in  any  other  work  known  to  me, 
My  judgment  may  not  be  trustworthy,  but  after  reading 
with  care  Mr.  Mivart’s  book,  and  comparing  each  section 
with  what  I  have  said  on  the  same  head,  I  never  before 
felt  so  strongly  convinced  of  the  general  truth  of  the  con¬ 
clusions  here  arrived  at,  subject,  of  course,  in  so  intricate 
a  subject,  to  much  partial  error. 

.  All  Mr.  MivarGs  objections  will  be,  or  have  been,  con¬ 
sidered  in  the  present  volume.  The  one  new  point  which 
appears  to  have  struck  many  readers  is,  “  That  natural 
selection  is  incompetent  to  account  for  the  incipient  stages 
of  useful  structures.”  This  subject  is  intimately  connected 
with  that  of  the  gradation  of  the  characters,  often 
accompanied  by  a  change  of  function,  for  instance,  the 
conversion  of  a  swim-bladder  into  lungs,  points  which 
were  discussed  in  the  last  chapter  under  two  headings. 
Nevertheless,  I  will  here  consider  in  some  detail  several  of 
the  cases  advanced  by  Mr.  Mivart,  selecting  those  which 
are  the  most  illustrative,  as  want  of  space  protrents  me 
from  considering  all. 

The  giraffe,  by  its  lofty  stature,  much  elongated  neck, 
fore  legs,  head  and  tongue,  has  its  whole  frame  beautifully 
adapted  for  browsing  on  the  higher  branches  of  trees.  It 
can  thus  obtain  food  beyond  the  reach  of  the  other  Ungulate 


2J0  MISCELLANEOUS  OBJECTIONS  TO  THE 

or  hoofed  animals  inhabiting  the  same  country;  and  this 
must  be  a  great  advantage  to  it  during  dearths.  The  Mata 
cattle  in  South  America  show  us  how  small  a  difference  in 
structure  may  make,  during  such  periods,  a  gi  eat  differ¬ 
ence  in  preserving  an  animal *s  life.  .These  cattle  can  bi  o\v  se 
as  well  as  others  on  grass,  but  from  the  projection  of.  the 
lower  jaw  they  cannot,  during  the  often  recuri  cut  di  oughts, 
browse  on  the  twigs  of  trees,  reeds,  etc.,  to  which  food  t  le 
common  cattle  and  horses  are  then  driven;  so  that  at 
these  times  the  Matas  perish,  if  not  fed  by  their 
owners.  Before  coming  to  Mr.  Mivart’s  objections, 

it  may  be  well  to  explain  once  again  how  natural 
selection  will  act  in  all  ordinary  cases.  Man  has 
modified  some  of  his  animals,  without  necessanly  having 
attended  to  special  points  of  structure,  by  simply  pre- 
serving  and  breeding  from  the  fleetest  individuals,  as  with 
the  race-horse  and  greyhound,  or  as  with  the  game-cock, 
by  breeding  from  the  victorious  birds.  So  undermature  with 
the  nascent  giraffe,  the  individuals  which  were  the  highest 
browsers  and  were  able  during  dearths  to  reach  even  an 
inch  or  two  above  the  others,  will  often  have  been  pre¬ 
served;  for  they  will  have  roamed  over  the  whole  country 
in  search  of  food.  That  the  individuals  of  the  same  species 
often  differ  slightly  in  the  relative  lengths  of  all  their  parts 
may  be  seen  in  many  works  of  natural  history,  in  which 
careful  measurements  are  given.  These  slight  proportional 
differences,  due  to  the  laws  of  growth  and  variation,  are 
not  of  the  slightest  use  or  importance  to  most  species.  But 
it  will  have  been  otherwise  with  the  nascent  giraffe,  con¬ 
sidering  its  probable  habits  of  life;  for  those  individuals 
which  bad  some  one  part  or  several  parts  of  their  bodies 
rather  more  elongated  than  usual,  would  generally  have 
survived.  These  will  have  intercrossed  and  left  offspring, 
either  inheriting  the  same  bodily  peculiarities,  or  with  a 
tendency  to  vary  again  in  the  same  manner  ;  while  the 
individuals  less  favored  in  the  same  respects  will  have 

been  the  most  liable  to  perish. 

We  here  see  that  there  is  no  need  to  separate  single  pairs, 
as  man  does,  when  he  methodically  improves  a  breed:  natu¬ 
ral  selection  will  preserve  and  thus  separate  all  the  supenor 
individuals,  allowing  them  freely  to  intercross,  and  will 
destroy  all  the  inferior  individuals.  By  this  process  long- 


|  THEORY  OF  HA  TUT  A  L  SELECTIO  H.  211 

continue*!,  which  exactly  corresponds  with  what  I  have 
called  unconscious  selection  by  man,  combined,  no  doubt, 
m  a  most  important  manner  with  the  inherited  effects  of 
the  increased  use  of  parts,  it  seems  to  me  almost  certain 
that  an  ordinary  hoofed  quadruped  might  be  converted 
into  a  giraffe. 

To  this  conclusion  Mr.  Mivart  brings  forward  two  ob¬ 
jections,  One  is  that  the  increased  size  of  the  body  would 
obviously  require  an  increased  supply  of  food,  and  he  con¬ 
siders  it  as  “  very  problematical  whether  the  disadvantages 
thence  arising  would  not,  in  times  of  scarcity,  more  than 
counterbalance  the  advantages.”  But  as  the  giraffe  does 
actually  exist  in  large  numbers  in  Africa,  and  as  some  of  the 
largest  antelopes  in  the  world,  taller  than  an  ox,  abound 
theie,  why  should  we  doubt  that,  as  far  as  size  is  concerned, 
intermediate  gradations  could  formerly  have  existed  there, 
subjected  as  now  to  severe  dearths.  Assuredly  the  being 
able  to  leach,  at  each  stage  of  increased  size,  to  a  supply 
of  food,  left  untouched  by  the  other  hoofed  quadrupeds  of 
the  country,  would  have  been  of  some  advantage  to  the 
nascent  giraffe.  Nor  must  we  overlook  the  fact,  that  in¬ 
creased  bulk  would  act  as  a  protection  against  almost  all 
beasts  of  prey  excepting  the  lion;  and  against  this  animal, 
its  tall  neck— —and  the  taller  the  better — would,  as  Mr. 
Chauncey  AY  right  has  remarked,  serve  as  a  watch-tower. 
It  is  from  this  cause,  as  Sir  S.  Baker  remarks,  that  no 
animal  is  more  difficult  to  stalk  than  the  giraffe.  This 
animal  also  uses  its  long  neck  as  a  means  of  offence  or  de¬ 
fence,  by  violently  swinging  its  head  armed  with  stump- 
lke  hoi  ns.  I  he  preservation  of  each  species  can  rarely  be 
determined  by  any  one  advantage,  but  by  the  union  of' all 
great  and  small. 

Mi.  Mivart  then  asks  (and  this  is  his  second  objection), 
i  natuial  selection  be  so  potent,  and  if  high  browsing  be 
so  great  an  advantage,  why  has  not  any  other  hoofed  quad¬ 
ruped  acquired  a  long  neck  and  lofty  stature,  besides  the 
giraffe,  and,,  in  a  lesser  degree,  the  camel,  guanaco  and 
in ac rau c heni a?  Or,  again,  why  has  not  any  member  of 
the  group  acquired  a  long  proboscis?  With  respect  to 
bouth  Africa,  which  was  formerly  inhabited  by  numerous 
herds  of  the  giraffe,  the  answer  is  not  difficult,  and  can 
best  be  given  by  an  illustration.  In  every  meadow  in 


212 


MISCELLANEOUS  OBJECTIONS  TO  THE 


England,  in  which  trees  grow,  we  see  the  lower  branches 
trimmed  or  planed  to  an  exact  level  by  the  browsing  of  the 
horses  or  cattle;  and  what  advantage  would  it  be,  for  in¬ 
stance,  to  sheep,  if  kept  there,  to  acquire  slightly  longer 
necks?  In  every  district  some  one  kind  of  animal  will 
almost  certainly  t>e  able  to  browse  higher  than  the  others; 
and  it  is  almost  equally  certain  that  this  one  kind  alone 
could  have  its  neck  elongated  for  this  purpose,  through 
natural  selection  and  the  eifects  of  increased  use.  In 
South  Africa  the  competition  for  browsing  on  the  higher 
branches  of  the  acacias  and  other  trees  must  be  between 
giraffe  and  giraffe,  and  not  with  the  other  ungulate 
animals. 

Why,  in  other  quarters  of  the  world,  various  animals 
belonging  to  this  same  order  have  not  acquired  either  an 
elongated  neck  or  a  proboscis,  cannot  be  distinctly 
answered;  but  it  is  as  unreasonable  to  expect  a  distinct 
answer  to  such  a  question  as  why  some  event  in  the  history 
of  mankind  did  not  occur  in  one  country  while  it  did  in 
another.  We  are  ignorant  with  respect  to  the  conditions 
which  determine  the  numbers  and  range  of  each  species, 
and  we  cannot  even  conjecture  what  changes  of  structure 
would  be  favorable  to  its  increase  in  some  new  country. 
We  can,  however,  see  in  a  general  manner  that  various 
causes  might  have  interfered  with  the  development  of  a 
long  neck  or  proboscis.  To  reach  the  foliage  at  a  consid¬ 
erable  height  (without  climbing,  for  which  hoofed  animals 
are  singularly  ill-constructed)  implies  greatly  increased 
bulk  of  body;  and  we  know  that  some  areas  support  singu¬ 
larly  few  large  quadrupeds,  for  instance  South  America, 
though  it  is  so  luxuriant,  while  South  Africa  abounds 
with  them  to  an  unparalleled  degree.  Why  this  should  be 
so  we  do  not  know;  nor  why  the  later  tertiary  periods 
should  have  been  much  more  favorable  for  their  existence 
than  the  present  time.  Whatever  the  causes  may  have 
been,  we  can  see  that  certain  districts  and  times  would  have 
been  much  more  favorable  than  others  for  the  development 
of  so  large  a  quadruped  as  the  giraffe. 

In  order  that  an  animal  should  acquire  some  structure 
specially  and  largely  developed,  it  is  almost  indispensable 
that  several  other  parts  should  be  modified  and  coadapted. 
Although  every  part  of  the  Dody  varies  slightly,  it  does  not 


TIIEOR  Y  OF  NA  TURA  L  SELECTION.  213 

follow  that  the  necessary  parts  should  always  vary  in  the 
right  direction  and  to  the  right  degree.  With  the  differ¬ 
ent  species  of  our  domesticated  animals  we  know  that  the 
parts  vary  in  a  different  manner  and  degree,  and  that  some 
species  are  much  more  variable  than  others.  Even  if  the 
fitting  variations  did  arise,  it  does  not  follow  that  natural 
selection  would  be  able  to  act  on  them  and  produce  a 
structure  which  apparently  would  be  beneficial  to  the  spe¬ 
cies.  Foi  instance,  if  the  number  of  individuals  existing 
m  a  country  is  determined  chiefly  through  destruction  by 
beasts  of  prey — by  external  or  internal  parasites,  etc. — as 
seems  often  to  be  the  case,  then  natural  selection  will  be 
able  to  do  little,  or  will  be  greatly  retarded,  in  modifying 
any  paiticular  structure  for  obtaining  food.  Lastlv,  nat- 
111  al  selection  is  a  slow  process,  and  the  same  favorable 
conditions  must  long  endure  in  order  that  any  marked 
effect  should  thus  be  produced.  Except  by  assigning  such 
general  and  vague  reasons,  we  cannot  explain  why,  in 
many  quarters  of  the  world,  hoofed  quadrupeds  have  not 
acquired  much  elongated  necks  or  other  means  for  brows¬ 
ing  on  the  higher  branches  of  trees. 

Objections  of  the  same  nature  as  the  foregoing  have  been 
advanced  by  many  writers.  In  each  case  various  causes, 
besides  the  general  ones  just  indicated,  have  probably  in¬ 
terfered  with  the  acquisition  through  natural  selection  of 
structures,  which  it  is  thought  would  be  beneficial  to  cer¬ 
tain  species.  One  writer  asks,  why  has  not  the  ostrich 
acquired  the  power  of  flight?  But  a  moments  reflection 
will  show  what  an  enormous  supplv  of  food  would  be  nec¬ 
essary  to  give  to  this  bird  of  the  desert  force  to  movo  its 
huge  body  through  the  air.  Oceanic  islands  are  inhabited  by 
bats  and  seals,  but  by  no  terrestrial  mammals;  yet  as  some 
of  these  bats  are  peculiar  species,  they  must  have  long  in¬ 
habited  their  present  homes.  Therefore  Sir  C.  Lyell  asks, 
and  assigns  certain  reasons  in  answer,  why  have  not  seals 
and  bats  given  birth  on  such  islands  to  forms  fitted  to  live 
on  the  land  ?  But  seals  would  necessarily  be  first  converted 
into  terrestrial  carnivorous  animals  of  considerable  size, 
and  bats  into  terrestrial  insectivorous  animals;  for  the 
former  there  would  be  no  prey;  for  the  bats  ground-insects 
would  serve  as  food,  but  these  would  already  be  largely  preyed 
on  by  the  reptiles  or  birds,  which  first  colonize  and  abound 


214  MISCELLANEOUS  OBJECTIONS  TO  TEE 

on  most  oceanic  islands.  Gradations  of  structure,  with  each 
stage  beneficial  to  a  changing  species,  will  be  favored  only 
under  certain  peculiar  conditions.  A  strictly  terrestiial 
animal,  by  occasionally  hunting  for  food  in  shallow  water, 
then  in  streams  or  lakes,  might  at  last  be  converted  into 
an  animal  so  thoroughly  accjuatic  as  to  brave  the  open 
ocean.  But  seals  would  not  find  on  oceanic  islands  the 
conditions  favorable  to  their  gradual  reconversion  into  a 
terrestrial  form.  Bats,  as  formerly  shown,  probably  ac¬ 
quired  their  wings  by  at  first  gliding  through  the  air  from 
tree  to  tree,  like  the  so-called  flying  squirrels,  for  the  sake 
of  escaping  from  their  enemies,  or  for  avoiding  falls;  but 
when  the  power  of  true  flight  had  once  been  acquired,  it 
would  never  be  reconverted  back,  at  least  for  the  above 
purposes,  into  the  less  efficient  power  of  gliding  through 
the  air.  Bats,  might,  indeed,  like  many  birds,  have  had 
their  wings  greatly  reduced  in  size,  or  completely  lost, 
through  disuse;  but  in  this  case  it  would  be  necessary  that 
they  should  first  have  acquired  the  power  of  running 
quickly  on  the  ground,  by  the  aid  of  their  hind  legs  alone, 
so  as  to  compete  with  birds  or  other  ground  animals;^  and 
for  such  a  change  a  bat  seems  singularly  ill-fitted,  GLhese 
conjectural  remarks  have  been  made  merely  to  show  that 
a  transition  of  structure,  with  each  step  beneficial,  is  a 
highly  complex  affair;  and  that  there  is  nothing  strange 
in  a  transition  not  having  occurred  in  any  particular  case. 

Lastly,  more  than  one  writer  has  asked  why  have  some 
animals  had  their  mental  powers  more  highly  developed 
than  others,  as  such  development  would  be  advantageous 
to  all?  Why  have  not  apes  acquired  the  intellectual 
powers  of  man?  Various  causes  could  be  assigned;  but  as 
they  are  conjectural,  and  their  relative  probability  can  not 
be  weighed,  it  would  be  useless  to  give  them.  A  definite 
answer  to  the  latter  question  ought  not  to  be  expected, 
seeing  that  no  one  can  solve  the  simpler  problem,  why,  of 
two  races  of  savages,  one  has  risen  higher  in  the  scale  of 
civilization  than  the  other;  and  this  apparently  implies  in¬ 
creased  brain  power. 

We  will  return  to  Mr.  MivarGs  other  objections.  Insects 
often  resemble  for  the  sake  of  protection  various  objects, 
such  as  green  or  decayed  leaves,  dead  twigs,  bits  of  lichen, 
flowers,  spines,  excrement  of  birds,  and  living  insects;  but 


THEORY  OF  NATURAL  SELECTION.  215 

to  this  latter  point  I  shall  hereafter  recur.  The  resem¬ 
blance  is  often  wonderfully  close,  and  is  not  confined  to 
color,  but  extends  to  form,  and  even  to  the  manner  in 
which  the  insects  hold  themselves.  The  caterpillars  which 
project  motionless  like  dead  twigs  from  the  bushes  on 
which  they  feed,  offer  an  excellent  instance  of  a  resem¬ 
blance  of  this  kind.  The  cases  of  the  imitation  of  such 
objects  as  the  excrement  of  birds,  are  rare  and  exceptional. 
On  this  head,  Mr.  Mivart  remarks,  “As,  according  to  Mr. 
Darwin's  theory,  there  is  a  constant  tendency  to  indefinite 
variation,  and  as  the  minute  incipient  variations  will  be  in 
all  directions,  they  must  tend  to  neutralize  each  other,  and 
at  first  to  form  such  unstable  modifications  that  it  is  diffi¬ 
cult,  if  not  impossible,  to  see  how  such  indefinite  oscilla¬ 
tions  of  infinitesimal  beginnings  can  ever  build  up  a  suffi¬ 
ciently  appreciable  resemblance  to  a  leaf,  bamboo,  or  other 
object,  for  natural  selection  to  seize  upon  and  perpetuate.” 

But  in  all  the  forgoing  cases  the  insects  in  their  original 
state  no  doubt  presented  some  rude  and  accidental  resem¬ 
blance  to  an  object  commonly  found  in  the  stations  fre¬ 
quented  by  them.  Nor  is  this  at  all  improbable,  consider¬ 
ing  the  almost  infinite  number  of  surrounding  objects  and 
the  diversity  in  form  and  color  of  the  hosts  of  insects 
which  exist.  As  some  rude  resemblance  is  necessary  for 
the  first  start,  we  can  understand  how  it  is  that  the  larger 
and  higher  animals  do  not  (with  the  exception,  as  far  as  I 
know,  of  one  fish)  resemble  for  the  sake  of  protection 
special  objects,  but  only  the  surface  which  commonly  sur¬ 
rounds  them,  and  this  chiefly  in  color.  Assuming  that  an 
insect  originally  happened  to  resemble  in  some  degree  a 
dead  twig  or  a  decayed  leaf,  and  that  it  varied  slightly  in 
many  ways,  then  all  the  variations  which  rendered  the  in¬ 
sect  at  all  more  like  any  such  object,  and  thus  favored  its 
escape,  would  be  preserved,  while  other  variations  would 
be  neglected  and  ultimately  lost;  or,  if  they  rendered  the 
insect  at  all  less  like  the  imitated  object,  they  would  be 
eliminated.  There  would  indeed  be  force  in  Mr.  Mivarffs 
objection,  if  we  were  to  attempt  to  account  for  the  above 
resemblances,  independently  of  natural  selection,  through 
mere  fluctuating  variability;  but  as  the  case  stands  there  is 
none. 

Nor  can  I  see  any  force  in  Mr.  Mivart’s  difficulty  with 


21(3  MISCELLANEOUS  OBJECTIONS  TO  TEE 

respect  to  “  the  last  touches  of  perfection  in  the  mimicry,* 
as  in  the  case  given  by  Mr.  Wallace,  of  a  walking-stick  in¬ 
sect  (Ceroxylus laceratus),  which  resembles  “a  stick  grown 
over  oy  a  creeping  moss  or  jungermannia.”  So  close  was 
this  resemblance,  that  a  native  Dyak  maintained  that  the 
foliaceous  excrescences  were  really  moss.  Insects  are  preyed 
on  by  birds  and  other  enemies  whose  sight  is  probably 
sharper  than  ours,  and  every  grade  in  resemblance  which 
aided  an  insect  to  escape  notice  or  detection,  would  tend 
toward  its  preservation;  and  the  more  perfect  the  resem¬ 
blance  so  much  the  better  for  the  insect.  Considering  the 
nature  of  the  differences  between  the  species  in  the  group 
which  includes  the  above  Ceroxylus,  there  is  nothing  im¬ 
probable  in  this  insect  having  varied  in  the  irregularities 
on  its  surface,  and  in  these  having  become  more  or  less 
green-colored;  for  in  every  group  the  characters  which 
differ  in  the  several  species  are  the  most  apt  to  vary,  while 
the  generic  characters,  or  those  common  to  all  the  species, 
are  the  most  constant. 

The  Greenland  whale  is  one  of  the  most  wonderful  am 
mals  in  the  world,  and  the  baleen,  or  whalebone,  one  of 
its  greatest  peculiarities.  The  baleen  consists  of  a  row,  on 
each  side  of  the  upper  jaw,  of  about  300  plates  or  laminae, 
which  stand  close  together  transversely  to  the  longer  axis 
of  the  mouth.  Within  the  main  row  there  are  some  subsid- 
iary  rows.  The  extremities  and  inner  margins  of  all  the 
plates  are  frayed  into  stiff  bristles,  which  clothe  the  whole 
gigantic  palate,  and  serve  to  strain  or  sift  the  water,  and 
thus  to  secure  the  minute  prey  on  which  these  great  ani¬ 
mals  subsist.  The  middle  and  longest  lamina  in  the  Green¬ 
land  whale  is  ten,  twelve,  or  even  fifteen  feet  in  length; 
but  in  the  different  species  of  Cetaceans  there  are  grada¬ 
tions  in  length;  the  middle  lamina  being  in  one  species, 
according  to  Scoresby,  four  feet,  in  another  three,  in 
another  eighteen  inches,  and  in  the  Balsenoptera  rostrata 
only  about  nine  inches  in  length.  The  quality  of  the 
whalebone  also  differs  in  the  different  species. 

With  respect  to  the  baleen,  Mr.  Mivart  remarks  that  if 
it  “  had  once  attained  such  a  size  and  development  as  to  be 
at  all  useful,  then  its  preservation  and  augmentation  within 
serviceable  limits  would  be  promoted  by  natural  selection 


THEORY  OF  NATURAL  SELECTION 


217 


alone.  But  how  to  obtain  the  beginning  of  such  useful 
development?”  In  answer,  it  may  be  asked,  why  should 
not  the  early  progenitors  of  the  whales  with  baieen  have 
possessed  a  mouth  constructed  something  like  the  lamel- 
lated  beak  of  a  duck?  Ducks,  like  whales,  subsist  by  sift¬ 
ing  the  mud  and  water ;  and  the  family  has  sometimes 
been  called  Criblatores ,  or  sifters.  I  hope  that  I  may  not 
be  misconstrued  into  saying  that  the  progenitors  of  whales 
did  actually  possess  mouths  lamellated  like  the  beak  of  a 
duck.  I  wish  only  to  show  that  this  is  not  incredible,  and 
that  the  immense  plates  of  baleen  in  the  Greenland  whale 
might  have  been  developed  from  such  lamellae  by  finely 
graduated  steps,  each  of  service  to  its  possessor. 

The  beak  of  a  shoveller-duck  (Spatula  clypeata)  is  a 
more  beautiful  and  complex  structure  than  the  mouth  of  a 
whale.  The  upper  mandible  is  furnished  on  each  side  (in 
the  specimen  examined  by  me)  with  a  row  or  comb  formed 
of  188  thin,  elastic  lamellae,  obliquely  bevelled  so  as  to  be 
pointed,  and  placed  transversely  to  the  longer  axis  of  the 
mouth.  They  arise  from  the  palate,  and  are  attached  by 
flexible  membrane  to  the  sides  of  the  mandible.  Those 
standing  toward  the  middle  are  the  longest,  being  about 
one-third  of  an  inch  in  length,  and  they  project  fourteen 
one-hundreths  of  an  inch  beneath  the  edge.  At  their 
bases  there  is  a  short  subsidiary  row  of  obliquely  transverse 
lamellae.  In  these  several  respects  they  resemble  the  plates 
of  baleen  in  the  mouth  of  a  whale.  But  toward  the  ex¬ 
tremity  of  the  beak  they  differ  much,  as  they  project  in¬ 
ward,  instead  of  straight  downward.  The  entire  head  of 
the  shoveller,  though  incomparably  less  bulky,  is  about  one- 
eighteenth  of  the  length  of  the  head  of  a  moderately  large 
Balaenoptera  rostrata,  in  which  species  the  baleen  is  only 
nine  inches  long;  so  that  if  we  were  to  make  the  head  of 
the  shoveller  as  long  as  that  of  the  Balaenoptera,  the  lam¬ 
ellae  would  be  six  inches  in  length,  that  is,  two-thirds  of 
the  length  of  the  baleen  in  this  species  of  whale.  The 
Lower  mandible  of  the  shoveller-duck  is  furnished  with 
lamellae  of  equal  length  with  these  above,  but  finer;  and  in 
being  thus  furnished  it  differs  conspicuously  from  the 
lower  jaw  of  a  whale,  which  is  destitute  of  baleen.  On 
the  other  hand,  the  extremities  of  these  lower  lamellae  are 
frayed  into  fine  bristly  points,  so  that  they  thus  curiously 


318 


MISCELLANEOUS  OBJECTIONS  TO  THE 


resemble  the  plates  of  baleen.  In  the  genus  Prion,  a 
member  of  the  distinct  family  of  the  Petrels,  the  upper 
mandible  alone  is  furnished  with  lamellae,  which  are  well 
developed  and  project  beneath  the  margin;  so  that  the 
beak  of  this  bird  resembles  in  this  respect  the  mouth  of  a 
whale. 

From  the  highly  developed  structure  of  the  shoveller  s 
beak  we  may  proceed  (as  I  have  learned  from  information 
and  specimens  sent  to  me  by  Mr.  Salvin),  without  any  great 
break,  as  far  as  fitness  for  sifting  is  concerned,  through 
the  beak  of  the  Merganetta  armata,  and  in  some  respects 
through  that  of  the  Aix  sponsa,  to  the  beak  of  the  common 
duck.  In  this  latter  species  the  lamellae  are  much  coarsei 
than  in  the  shoveller,  and  are  firmly  attached  to  the  sides 
of  the  mandible;  they  are  only  about  fifty  in  number  01 
each  side,  and  do  not  project  at  all  beneath  the  margin. 
They  are  square-topped,  and  are  edged  with  translucent, 
hardish  tissue,  as  if  for  crushing  food.  The  edges  of  the 
lower  mandible  are  crossed  by  numerous  fine  ridges,  which 
project  very  little.  Although  the  beak  is  thus  very  interim 
as  a  sifter  to  that  of  a  shoveller,  yet  this  bird,  as  every  one 
knows,  constantly  uses  it  for  this  purpose.  There  are 
other  species,  as  I  hear  from  Mr.  Salvin,  in  which  the 
lamellae  are  considerably  less  developed  than  in  the  commoc 
duck;  but  I  do  not  know  whether  they  use  their  beaks  for 
sifting  the  water. 

Turning  to  another  group  of  the  same  family.  In  the 
Egyptian  goose  (Chenalopex)  the  beak  closely  resembles, 
that  of  the  common  duck;  but  the  lamellas  are  not  so 
numerous,  nor  so  distinct  from  each  other,  nor.  do  they 
project  so  much  inward;  yet  this  goose,  as  I  am  informed 
by  Mr.  E.  Bartlett,  “  uses  its  bill  like  a  duck  by  throwing 
the  water  out  at  the  corners.”  Its  chief  food,  however,  is 
grass,  which  it  crops  like  the  common  goose.  In  this  latter 
bird  the  lamellae  of  the  upper  mandible  are  much  coarser 
than  in  the  common  duck,  almost  confluent,. about  twenty- 
seven  in  number  on  each  side,  and  terminating  upward  in 
teeth-like  knobs.  The  palate  is  also  covered  with  hard 
rounded  knobs.  The  edges  of  the  lower  mandible  are 
serrated  with  teeth  much  more  prominent,  coarser  and 
sharper  than  in  the  duck.  The  common  goose  does  not  sift 
the  water,  but  uses  its -beak  exclusively  for  tearing  or  cut- 


TBEOR  Y  OF  NA  TURAL  SELECTION.  210 

ting  herbage,  for  which  purpose  it  is  so  well  fitted  that  it 
can  crop  grass  closer  than  almost  any  other  animal.  There 
are  other  species  of  geese,  as  I  hear  from  Mr.  Bartlett,  in 
which  the  lamellae  are  less  developed  than  in  the  common 
goose. 

We  thus  see  that  a  member  of  the  duck  family,  with  a 
beak  constructed  like  that  of  a  common  goose  and  adapted 
solely  for  grazing,  or  even  a  member  with  a  beak  having 
less  well-developed  lamellae,  might  be  converted  by  small 
changes  into  a  species  like  the  Egyptian  goose — this  into 
one  like  the  common  duck — and,  lastly,  into  one  like  the 
shoveller,  provided  with  a  beak  almost  exclusively  adapted 
for  sifting  the  water;  for  this  bird  could  hardly  use  any 
part  of  its  beak,  except  the  hooked  tip,  for  seizing  or  tear¬ 
ing  solid  food.  The  beak  of  a  goose,  as  I  may  add,  might 
also  be  converted  by  small  changes  into  one  provided  with 
prominent,  recurved  teeth,  like  those  of  the  Merganser  (a 
member  of  the  same  family),  serving  for  the  widely  differ¬ 
ent  purpose  of  securing  live  fish. 

Returning  to  the  whales.  The  Hyperoodon  bidens  is 
destitute  of  true  teeth  in  an  efficient  condition,  but  its 
palate  is  roughened,  according  to  Lacepede,  with  small 
unequal,  hard  points  of  horn.  There  is.  therefore,  noth¬ 
ing  improbable  in  supposing  that  some  early  Cetacean  form 
was  provided  with  similar  points  of  horn  on  the  palate, 
but  rather  more  regularly  placed,  and  which,  like  the 
knobs  on  the  beak  of  the  goose,  aided  it  in  seizing  or  tear¬ 
ing  its  food.  If  so,  it  will  hardly  be  denied  that  the  points 
might  have  been  converted  through  variation  and  natural 
selection  into  lamellas  as  well-developed  as  those  of  the 
Egyptian  goose,  in  which  case  they  would  have  been  used 
both  for  seizing  objects  and  for  sifting  the  water;  then 
into  lamellce  like  those  of  the  domestic  duck;  and  so  on¬ 
ward,  until  they  became  as  well  constructed  as  those  cf  the 
shoveller,  in  which  case  they  would  have  served  exclusively 
as  a  sifting  apparatus.  Erom  this  stage,  in  which  the 
lamellas  would  be  two-thirds  of  the  length  of  the  plates  of 
baleen  in  the.  Balasnoptera  rostrata,  gradations,  which  may 
be  observed  in  still-existing  Cetaceans,  lead  us  onward  to 
tne  enormous  plates  oi  baleen  in  the  Greenland  whale. 
Noi  is  there,  the  least  reason  to  doubt  that  each  step  in 
this  scale  might  have  been  as  serviceable  to  certain  ancient 


220 


MISCELLANEOUS  OBJECTIONS  TO  THE 


Cetaceans,  with  the  functions  of  the  parts  slowly  changing 
during  the  progress  of  development,  as  are  the  gradations 
in  the  beaks  of  the  different  existing  members  of  the  duck- 
family.  We  should  bear  in  mind  that  each  species  of  duck 
is  subjected  to  a  severe  struggle  for  existence,  and  that  the 
structure  of  every  part  of  its  frame  must  be  well  adapted 
to  its  conditions  of  life. 

The  Pleuronectidae,  or  Flat-fish,  are  remarkable  for 
their  asymmetrical  bodies.  They  rest  on  one  side— in  the 
greater  number  of  species  on  the  left,  but  in  some  on  the 
right  side;  and  occasionally  reversed  adult  specimens 
occur.  The  lower,  or  resting- surface,  resembles  at  first 
sight  the  ventral  surface  of  an  ordinary  fish;  it  is  of  a  white 
color,  less  developed  in  many  ways  than  the  upper  side, 
with  the  lateral  fins  often  of  smaller  size.  But  the  eyes 
offer  the  most  remarkable  peculiarity;  for  they  are  both 
placed  on  the  upper  side  of  the  head.  During  early  youth, 
however,  they  stand  opposite  to  each  other,  and  the  whole 
body  is  then  symmetrical,  with  both  sides  equally  colored. 
Soon  the  eye  proper  to  the  lower  side  begins  to  glide 
slowly  round  the  head  to  the  upper  side;  but  does  not  pass 
right  through  the  skull,  as  was  formerly  thought  to  be 
the  case.  It  is  obvious  that  unless  the  lower  eye  did  thus 
travel  round,  it  could  not  be  used  by  the  fish  while  lying 
in  its  habitual  position  on  one  side.  The  lower  eye  would, 
also,  have  been  liable  to  be  abraded  by  the  sandy  bottom. 
That  the  Pleuronectidae  are  admirably  adapted  by  theii 
flattened  and  asymmetrical  structure  for  their  habits  of 
life,  is  manifest  from  several  species,  such  as  soles,  flound¬ 
ers,  etc.,  being  extremely  common.  The  chief  advantages 
thus  gained  seem  to  be  protection  from  their  enemies,  and 
facility  for  feeding  on  the  ground.  The  different  mem 
bers,  however,  of  the  family  present,  as  Schiodte  remarks, 
“a  long  series  of  forms  exhibiting  a  gradual  transition 
from  Hippoglossus  pinguis,  which  does  not  in  any  consid¬ 
erable  degree  alter  the  shape  in  which  it  leaves  the  ovum, 
to  the  soles,  which  are  entirely  thrown  to  one  side.” 

Mr.  Mivart  has  taken  up  this  case,  and  remarks  that  a 
sudden  spontaneous  transformation  in  the  position  of  the 
eyes  is  hardly  conceivable,  in  which  I  quite  agree  with  him. 
He  then  adds:  “  If  the  transit  was  gradual,  then  how  such 
transit  of  one  eye  a  minute  fraction  of  the  journey  toward 


THEORY  OF  NATURAL  SELECTION. 


221 


the  other  side  of  the  head  could  benefit  the  individual  is, 
indeed,  far  from  clear.  It  seems,  even,  that  such  an  in¬ 
cipient  transformation  must  rather  have  been  injurious.” 
But  ho  might  have  found  an  answer  to  this  objection  in 
the  excellent  observations  published  in  1867  by  Malm. 
The  Pleuronectidse,  while  very  young  and  still  symmetri¬ 
cal,  with  their  eyes  standing  on  opposite  sides  of  the  head, 
cannot  long  retain  a  vertical  position,  owing  to  the  exces¬ 
sive  depth  of  their  bodies,  the  small  size  of  their  lateral 
fins,  and  to  their  being  destitute  of  a  swim-bladder. 
Hence,  soon  growing  tired,  they  fall  to  the  bottom  on  one 
side.  While  thus  at  rest  they  often  twist,  as  Malm  ob¬ 
served,  the  lower  eye  upward,  to  see  above  them;  and  they 
do  this  so  vigorously  that  the  eye  is  pressed  hard  against 
the  upper  part  of  the  orbit.  The  forehead  between  the 
eyes  consequently  becomes,  as  could  be  plainly  seen,  tem¬ 
porarily  contracted  in  breadth.  On  one  occasion  Malm 
saw  a  young  fish  raise  and  depress  the  lower  eye  through 
an  angular  distance  of  about  seventy  degrees. 

We  should  remember  that  the  skull  at  this  early  age  is 
cartilaginous  and  flexible,  so  that  it  readily  yields  to  mus¬ 
cular  action.  It  is  also  known  with  the  higher  animals, 
even  after  early  youth,  that  the  skull  yields  and  is  altered 
in  shape,  if  the  skin  or  muscles  be  permanently  contracted 
through  disease  or  some  accident.  With  long-eared  rab¬ 
bits,  if  one  ear  flops  forward  and  downward,  its  weight 
drags  forward  all  the  bones  of  the  skull  on  the  same  side, 
of  which  I  have  given  a  figure.  Malm  states  that  the 
newly-hatched  young  of  perches,  salmon,  and  several  other 
symmetrical  fishes,  have  the  habit  of  occasionally  resting 
on  one  side  at  the  bottom;  and  he  has  observed  that  they 
often  then  strain  their  lower  eyes  so  as  to  look  upward; 
and  their  skulls  are  thus  rendered  rather  crooked.  These 
fishes,  however,  are  soon  able  to  hold  themselves  in  a  ver¬ 
tical  position,  and  no  permanent  effect  is  thus  produced. 
With  the  Pleuronectidae,  on  the  other  hand,  the  older  they 
grow  the  more  habitually  they  rest  on  one  side,  owing  to 
the  increasing  flatness  of*  their  bodies,  and  a  permanent 
effect  is  thus  produced  on  the  form  of  the  head,  and  on  the 
position  of  the  eyes.  Judging  from  analogy,  the  tendency 
to  distortion  would  no  doubt  be  increased  through  the 
principle  of  inheritance.  Schiodte  believes,  in  opposition 


222 


MISCELLANEOUS  OBJECTIONS  TO  THE 


to  some  other  naturalists,  that  the  Pleuronectidae  are  not 
quite  symmetrical  even  in  the  embryo;  and  if  this  be  so, 
we  could  understand  how  it  is  that  certain  species,  while 
young,  habitually  fall  over  and  rest  on  the  left  side,  and 
other  species  on  the  right  side.  Malm  adds,  in  confirma¬ 
tion  of  the  above  view,  that  the  adult  Trachypterus  arcti- 
cus,  which  is  not  a  member  of  the  Pleuronectidae,  rests  on 
its  left  side  at  the  bottom,  and  swims  diagonally  through 
the  water;  and  in  this  fish,  the  two  sides  of  the  head  are 
said  to  be  somewhat  dissimilar.  Our  great  authority  on 
Fishes,  Dr.  Gunther,  concludes  his  abstract  of  Malm’s 
paper,  by  remarking  that  “the  author  gives  a  very  simple 
explanation  of  the  abnormal  condition  of  the  Pleu- 
ronectoids.” 

We  thus  see  that  the  first  stages  of  the  transit  of  the 
eye  from  one  side  of  the  head  to  the  other,  which  Mr. 
Mivart  considers  would  be  injurious,  may  be  attributed 
to  the  habit,  no  doubt  beneficial  to  the  individual  and 
to  the  species,  of  endeavoring  to  look  upward  with  both 
eyes,  while  resting  on  one  side  at  the  bottom.  We  may 
also  attribute  to  the  inherited  effects  of  use  the  fact  of  the 
mouth  in  several  kinds  of  flat-fish  being  bent  toward  the 
lower  surface,  with  the  jaw  bones  stronger  and  more  effect¬ 
ive  on  this,  the  eyeless  side  of  the  head,  than  on  the  other, 
for  the  sake,  as  Dr.  Traquair  supposes,  of  feeding  with  ease 
on  the  ground.  Disuse,  on  the  other  hand,  will  account 
for  the  less  developed  condition  of  the  whole  inferior  half 
of  the  body,  including  the  lateral  fins;  though  Yarrel 
thinks  that  the  reduced  size  of  these  fins  is  advantageous 
to  the  fish,  as  “  there  is  so  much  less  room  for  their  action, 
than  with  the  larger  fins  above.”  Perhaps  the  lesser 
number  of  teeth  in  the  proportion  of  four  to  seven  in  the 
upper  halves  of  the  two  jaws  of  the  plaice,  to  twenty-five 
to  thirty  in  the  lower  halves,  may  likewise  be  accounted 
for  by  disuse.  From  the  colorless  state  of  the  ventral  sur¬ 
face  of  most  fishes  and  of  many  other  animals,  we  may 
reasonably  suppose  that  the  absence  of  color  in  flat-fish  on 
the  side,  whether  it  be  the  right  or  left,  which  is  under¬ 
most,  is  due  to  the  exclusion  of  light.  But  it  cannot  be 
supposed  that  the  peculiar  speckled  appearance  of  the 
upper  side  of  the  sole,  so  like  the  sandy  bed  of  the  sea,  or 
the  power  in  some  species,  as  recently  shown  by  Pouchet, 


THEORY  OF  NATURAL  SELECTION. 


223 


of  changing  their  color  in  accordance  with  the  surround¬ 
ing  surface,  or  the  presence  of  bony  tubercles  on  the  upper 
side  of  the  turbot,  are  due  to  the  action  of  the  light. 
Here  natural  selection  has  probably  come  into  play,  as  well 
as  in  adapting  the  general  shape  of  the  body  of  these 
fishes,  and  many  other  peculiarities,  to  their  habits  of  life. 
We  should  keep  in  mind,  as  I  have  before  insisted,  that 
the  inherited  effects  of  the  increased  use  of  parts,  and  per¬ 
haps  of  their  disuse,  will  be  strengthened  by  natural  selec¬ 
tion.  For  all  spontaneous  variations  in  the  right  direc¬ 
tion  will  thus  be  preserved;  as  will  those  individuals  which 
inherit  in  the  highest  degree  the  effects  of  the  increased 
and  beneficial  use  of  any  part.  How  much  to  attribute  in 
each  particular  case  to  the  effects  of  use,  and  how  much  to 
natural  selection,  it  seems  impossible  to  decide. 

I  may  give  another  instance  of  a  structure  which  appar¬ 
ently  owes  its  origin  exclusively  to  use  or  habit.  The 
extremity  of  the  tail  in  some  American  monkej's  has  been 
converted  into  a  wonderfully  perfect  prehensile  organ,  and 
serves  as  a  fifth  hand.  A  reviewer,  who  agrees  with  Mr. 
Mivart  in  every  detail,  remarks  on  this  structure:  “It  is 
impossible  to  believe  that  in  any  number  of  ages  the  first 
slight  incipient  tendency  to  grasp  could  preserve  the  lives 
of  the  individuals  possessing  it,  or  favor  their  chance  of 
having  and  of  rearing  offspring.”  But  there  is  no  neces¬ 
sity  for  any  such  belief.  Habit,  and  this  almost  implies 
that  some  benefit  great  or  small  is  thus  derived,  would  in 
all  probability  suffice  for  the  work.  Brehm  saw  the  young 
of  an  African  monkey  (Cercopithecus)  clinging  to  the 
under  surface  of  their  mother  by  their  hands,  and  at  the 
same  time  they  hooked  their  little  tails  round  that  of  their 
mother.  Professor  Henslow  kept  in  confinement  some 
harvest  mice  (Mus  messorius)  which  do  not  pos¬ 
sess  a  structurally  prehensive  tail;  but  he  frequently 
observed  that  they  curled  their  tails  round  the 
branches  of  a  bush  placed  in  the  cage,  and  thus  aided 
themselves  in  climbing.  I  have  received  an  analo¬ 
gous  account  from  Dr.  Gunther,  who  has  seen  a 
mouse  thus  suspend  itself.  If  the  harvest  mouse  had 
been  more  strictly  arboreal,  it  would  perhaps  have 
had  its  tail  rendered  structurally  prehensile,  as  is 
the  case  with  some  members  of  the  same  order.  Why 


MISCELLANEOUS  OBJECTIONS  TO  THE 


224 

Cercopithecus,  considering  its  habits  while  young,  has  not 
become  thus  provided,  it  would  be  difficult  to  say.  It  is, 
however,  possible  that  the  long  tail  of  this  monkey  may  be 
of  more  service  to  it  as  a  balancing  organ  in  making  its 
prodigious  leaps,  than  as  a  prehensile  organ. 

The  mammary  glands  are  common  to  the  whole  class  of 
mammals,  and  are  indispensable  for  their  existence;  they 
must,  therefore,  have  been  developed  at  an  extremely 
remote  period,  and  we  can  know  nothing  positively  about 
their  manner  of  development.  Mr.  Mivart  asks:  “Is  it 
conceivable  that  the  young  of  any  animal  was  ever  saved 
from  destruction  by  accidentally  sucking  a  drop  of  scarcely 
nutritious  fluid  from  an  accidentally  hypertrophied  cuta¬ 
neous  gland  of  its  mother?  And  even  if  one  was  so,  what 
chance  was  there  of  the  perpetuation  of  such  a  variation  V* 
But  the  case  is  not  here  put  fairly.  It  is  admitted  by  most 
evolutionists  that  mammals  are  descended  from  a  marsu¬ 
pial  form;  and  if  so,  the  mammary  glands  will  have  been 
at  first  developed  within  the  marsupial  sack.  In  the  case 
of  the  fish  (Hippocampus)  the  eggs  are  hatched,  and  the 
young  are  reared  for  a  time,  within  a  sack  of  this  nature; 
and  an  American  naturalist,  Mr.  Lockwood,  believes  from 
what  he  has  seen  of  the  development  of  the  young,  that 
they  are  nourished  by  a  secretion  from  the  cutaneous 
glands  of  the  sack.  Now,  with  the  early  progenitors  of 
mammals,  almost  before  they  deserved  to  be  thus  desig¬ 
nated,  is  it  not  at  least  possible  that  the  young  might  have 
been  similiarly  nourished?  And  in  this  case,  the  individu¬ 
als  which  secreted  a  fluid,  in  some  degree  or  manner  the 
most  nutritious,  so  as  to  partake  of  the  nature  of  milk, 
would  in  the  long  run  have  reared  a  larger  number  of  well- 
nourished  offspring,  than  would  the  individuals  which 
secreted  a  poorer  fluid;  and  thus  the  cutaneous  glands, 
which  are  the  homologues  of  the  mammary  glands,  would 
have  been  improved  or  rendered  more  effective.  It  accords 
with  the  widely  extended  principle  of  specialization,  that 
the  glands  over  a  certain  space  of  the  sack  should  have 
become  more  highly  developed  than  the  remainder;  and 
they  would  then  have  formed  a  breast,  but  at  first  without 
a  nipple,  as  we  see  in  the  Ornithorhyncus,  at  the  base  of 
the  mammalian  series.  Through  what  agency  the  glands 


THEOR Y  OF  NATURAL  SEL EGTIO N.  225 

over  a  certain  space  became  more  highly  specialized  than 
the  others,  I  will  not  pretend  to  decide,  whether  in  part 
through  compensation  of  growth,  the  effects  of  use,  or  of 
natural  selection. 

The  development  of  the  mammary  glands  would  have 
been  of  no  service,  and  could  not  have  been  affected 
through  natural  selection,  unless  the  young  at  the  same 
time  were  able  to  partake  of  the  secretion.  There  is  no 
greater  difficulty  in  understanding  how  young  mammals 
have  mstinctiveiy  learned  to  suck  the  breast,  than  in  under* 
standing  how  unhatched  chickens  have  learned  to  break  the 
egg-shell  by  tapping  against  it  with  their  specially  adapted 
beaks;  or  how  a  few  hours  after  leaving  the  shell  thev  have 
learned  to  pick  up  grains  of  food.  In  such  cases  the  most 
probable  solution  seems  to  be,  that  the  habit  was  at  first 
acquired  by  practice  at  a  more  advanced  age,  and  after¬ 
ward  transmitted  to  the  offspring  at  an  earlier  age.  But  the 
young  kangaroo  is  said  not  to  suck,  only  to  cling  to  the 
nipple  of  its  mother,  who  has  the  power  of  injecting  milk 
into  the  mouth  of  her  helpless,  half-formed  offspring.  On 
this  head  Mr.  Mivart  remarks:  “Did  no  special  provision 
exist,  the  young  one  must  infallibly  be  choked  by  the  in¬ 
trusion  of  the  milk  into  the  wind-pipe.  But  there  is  a 
special  provision.  .  The  larynx  is  so  elongated  that  it  rises 

UP  u i  j  Pos^er^or  end  of  the  nasal  passage,  and  is  thus 
enabled  to  give  free  entrance  to  the  air  for  the  lungs,  while 
the  milk  passes  harmlessly  on  each  side  of  this  elongated 
larynx,  and  so  safely  attains  the  gullet  behind  it.”  Mr. 
Mivart  then  asks  how  did  natural  selection  remove  in  the 
adult  kangaroo  (and  in  most  other  mammals,  on  the  assump¬ 
tion  that  they  are  descended  from  a  marsupial  form),  “this 
at  least  perfectly  innocent  and  harmless  structure?”  It 
may  be  suggested  in  answer  that  the  voice,  which  is  cer¬ 
tainly  of  high  importance  to  many  animals,  could  hardly 
have  been  used  with  full  force  as  long  as  the  larynx  en¬ 
tered  the  nasal  passage;  and  Professor  Flower  has  suggested 
to  me  that  this  structure  would  have  greatly  interfered  with 
an  animal  swallowing  solid  food. 

We  will  now  turn  for  a  short  space  to  the  lower  divisions 
of  the  animal  kingdom.  The  Echinodermata  (star-fishes, 
sea-urchins,  etc.)  are  furnished  with  remarkable  organs, 
called  pedicellarias,  which  consist,  when  well  developed,  of 


226  MISCELLANEOUS  OBJECTIONS  TO  THE 

a  tridactvle  forceps— that  is,  of  one  formed  of  three  ser- 
rated  arms,  neatly  fitting  together  and  placed  on i  the 
summit  of  a  flexible  stem,  moved  by  muscles,  these  tor- 
ceps  can  seize  firmly  hold  of  any  object;  and  Alexander 
Agassiz  has  seen  an  Echinus  or  sea-urchin  rapidly  passing 
particles  of  excrement  from  forceps  to  forceps  down  certain 
lines  of  its  body,  in  order  that  its  shell  should  not  be 
fouled.  But  there  is  no  doubt  that  besides  removing  dirt 
of  all  kinds,  they  subserve  other  functions;  and  one  ot 
these  apparently  is  defence. 

With  respect  to  these  organs,  Mr.  Mivart,  as  on  so  many 
previous  occasions,  asks:  “  What  would  be  the  utility  of 
the  first  rudimentary  beginnings  of  such  structures,  ana 
how  could  such  insipient  buddings  have  ever  preserved  the 
life  of  a  single  Echinus?”  He  adds,  “not  even  the  sudden 
development  of  the  snapping  action  could  have  been  bene¬ 
ficial  without  the  freely  movable  stalk,  nor  could  the 
latter  have  been  efficient  without  the  snapping  jaws  yet 
no  minute,  merely  indefinite  variations  could  simultane¬ 
ously  evolve  these  complex  co-ordinations  of  structure;  to 
deny  this  seems  to  do  no  less  than  to  affirm  a  startling 
paradox.”  Paradoxical  as  this  may  appear  to  Mr.  Mivait, 
tridactyle  forcepses,  immovably  fixed  at  the  base,  but  capa¬ 
ble  of  a  snapping  action,  certainly  exist  on  some  star-fishes; 
and  this  is  intelligible  if  they  serve,  at  least  m  part,  as  a 
means  of  defence.  Mr.  Agassiz,  to  whose  great  kindness 
lam  indebted  for  much  information  on  the  subject,  in¬ 
forms  me  that  there  are  other  star-fishes,  m  which  one  oi 
the  three  arms  of  the  forceps  is  reduced,  to  a  support  lor 
the  other  two;  and  again,  other  genera  m  which  the  thud 
arm  is  completely  lost.  In  Ecliinoneus  the  shell  is  de¬ 
scribed  by  M.  Perrier  as  bearing  two  kinds  ot  pediceilai  iae, 
one  resembling  those  of  Echinus,  and  the  other  those  oi 
Spatangus;  and  such  cases  are  always  interesting  as  attord- 
ing  the  means  of  apparently  sudden  transitions,  through 
the  abortion  of  one  of  the  two  states  of  an  oigan. 

With  respect  to  the  steps  by  which  these  curious  organs 
have  been  evolved,  Mr.  Agassiz  infers  from  Ins  own  re¬ 
searches  and  those  of  Mr.  Muller,  that  both  m  star-fishes 
and  sea-urchins  the  pedicellariae  must  undoubtedly  be 
looked  at  as  modified  spines.  This  may  be  inferred  f i°ni 
their  manner  of  development  in  the  individual,  as  well  as 


THEORY  OF  NATURAL  SELECTION. 


227 


from  a  long  and  perfect  series  of  gradations  in  different 
species  and  genera,  from  simple  granules  to  ordinary 
spines,  to  perfect  tridactyle  pedicellariae.  The  gradation 
extends  even  to  the  manner  in  which  ordinary  spines  and 
The  pedicellariae,  with  their  supporting  calcareous  rods,  are 
articulated  to  the  shell.  In  certain  genera  of  star-fishes, 
“  the  very  combinations  needed  to  show  that  the  pedicel¬ 
lariae  are  only  modified  branching  spines  ”  may  be  found. 
Thus  we  have  fixed  spines,  with  three  equi-distant,  serrated, 
movable  branches,  articulated  to  near  their  bases;  and 
higher  up,  on  the  same  spine,  three  other  movable 
branches.  Now  when  the  latter  arise  from  the  summit  of 
a  spine  they  form,  in  fact,  a  rude  tridactyle  pedicellariae, 
and  such  may  be  seen  on  the  same  spine  together  with  the 
three  lower  branches.  In  this  case  the  identity  in  nature 
between  the  arms  of  the  pedicellariae  and  the  movable 
branches  of  a  spine,  is  unmistakable.  It  is  generally 
admitted  that  the  ordinary  spines  serve  as  a  protection; 
and  if  so,  there  can  be  no  reason  to  doubt  that  those  fur¬ 
nished  with  serrated  and  movable  branches  likewise  serve 
for  the  same  purpose;  and  they  would  thus  serve  still  more 
effectively  as  soon  as  by  meeting  together  they  acted  as  a 
prehensile  or  snapping  apparatus.  Thus  every  gradation, 
from  an  ordinary  fixed  spine  to  a  fixed  pedicellariae,  would 
be  of  service. 

In  certain  genera  of  star-fishes  these  organs,  instead  of 
being  fixed  or  borne  on  an  immovable  support,  are  placed  on 
the  summit  of  a  flexible  and  muscular,  though  short,  stem; 
and  in  this  case  they  probably  subserve  some  additional 
function  besides  defence.  In  the  sea-urchins  the  steps  can 
be  followed  by  which  a  fixed  spine  becomes  articulated  to 
the  shell,  and  is  thus  rendered  movable.  I  wish  I  had 
space  here  to  give  a  fuller  abstract  of  Mr.  Agassiz’s  inter¬ 
esting  observations  on  the  development  of  the  pedicellariae. 
All  possible  gradations,  as  he  adds,  may  likewise  be  found 
between  the  pedicellariae  of  the  star-fishes  and  the  hooks 
of  the  Ophiurians,  another  group  of  the  Echinodermata; 
and  again  between  the  pedicellariae  of  sea-urchins  and  the 
anchors  of  the  Holothuriae,  also  belonging  to  the  same 
great  class. 

Certain  compound  animals,  or  zoophytes,  as  they  have 


228 


MISCELLANEOUS  OBJECTIONS  TO  TEE 


been  termed,  namely  the  Polyzoa,  are  provided  with  curious 
organs  called  avicularia.  These  differ  much  in  structure 
in  the  different  species.  In  their  most  perfect  condition 
they  curiously  resemble  the  head  and  beak  of  a  vulture  in 
miniature,  seated  on  a  neck  and  capable  of  movement,  as 
is  likewise  the  lower  jaw  or  mandible.  In  one  species  ob¬ 
served  by  me,  all  the  avicularia  on  the  same  branch  often 
moved  simultaneously  backward  and  forward,  with  the 
lower  jaw  widely  open,  through  an  angle  of  about  90 
degrees,  in  the  course  of  five  seconds;  and  their  movement 
caused  the  whole  polyzoary  to  tremble.  When  the  jaws 
are  touched  with  a  needle  they  seize  it  so  firmly  that  the 
branch  can  thus  be  shaken. 

Mr.  Mivart  adduces  this  case,  chiefly  on  account  of  the 
supposed  difficulty  of  organs,  namely  the  avicularia  of 
the  Polyzoa  and  the  pedicellariae  of  the  Echinodermata, 
which  he  considers  as  “  essentially  similar,”  having  been 
developed  through  natural  selection  in  widely  distinct 
divisions  of  the  animal  kingdom.  But,  as  far  as  struct¬ 
ure  is  concerned,  1  can  see  no  similarity  between  tridac- 
tyle  pedicellariae  and  avicularia.  The  latter  resembles 
somewhat  more  closely  the  chelae  or  pincers  of  Crusta¬ 
ceans;  and  Mr.  Mivart  might  have  adduced  with  equal 
appropriateness  this  resemblance  as  a  special  difficulty,  or 
even  their  resemblance  to  the  head  and  beak  of  a  bird. 
The  avicularia  are  believed  by  Mr.  Busk,  Dr.  Smitt  and 
Dr.  Nitsche — naturalists  who  have  carefully  studied  this 
gr0Up — to  be  homologous  with  the  zooids  and  their  cells 
which  compose  the  zoophyte,  the  moveable  lip  or  lid  of  the 
cell  corresponding  with  the  lower  and  movable  mandible  of 
the  avicularium.  Mr.  Busk,  however,  does  not  know  of 
any  gradations  now  existing  between  a  zooid  and  an  avicu- 
larium.  It  is  therefore  impossible  to  conjecture  by  what 
serviceable  gradations  the  one  could  have  been  converted 
into  the  other,  but  it  by  no  means  follows  from  this  that 
such  gradations  have  not  existed. 

As  the  chelae  of  Crustaceans  resemble  in  some  degree  the 
avicularia  of  Polyzoa,  both  serving  as  pincers,  it  may  be 
worth  while  to  show  that  with  the  former  a  long  series  of 
serviceable  gradations  still  exists.  In  the  first  and  simplest 
stage,  the  terminal  segment  of  a  limb  shuts  down  either  on 
the  sauare  summit  of  the  broad  penultimate  segment,  or 


THEORY  OF  NATURAL  SELECTION,  229 

against  one  whole  side,  and  is  thus  enabled  to  catch  hold 
of  an  object,  but  the  limb  still  serves  as  an  organ  of  loco¬ 
motion.  We  next  find  one  corner  of  the  broad  penulti¬ 
mate  segment  slightly  prominent,  sometimes  furnished 
with  irregular  teeth,  and  against  these  the  terminal  seg¬ 
ment  shuts  down.  By  an  increase  in  the  size  of  this  pro¬ 
jection,  with  its  shape,  as  well  as  that  of  the  terminal 
segment,  slightly  modified  and  improved,  the  pincers  are 
rendered  more  and  more  perfect,  until  we  have  at  last  an 
instrument  as  efficient  as  the  chelae  of  a  lobster.  And  all 
these  gradations  can  be  actually  traced. 

Besides  the  avicularia,  the  polyzoa  possess  curious  organs 
called  vibracula.  These  generally  consist  of  long  bristles, 
capable  of  movement  and  easily  excited.  In  one  species 
examined  by  me  the  vibracula  were  slightly  curved  and 
serrated  along  the  outer  margin,  and  all  of  them  on  the 
same  polyzoary  often  moved  simultaneously;  so  that,  acting 
like  long  oars,  they  swept  a  branch  rapidly  across  the  object- 
glass  of  my  microscope.  When  a  branch  was  placed  on  its 
face,  the  vibracula  became  entangled,  and  they  made  vio¬ 
lent  efforts  to  free  themselves.  They  are  supposed  to  serve 
as  a  defence,  and  may  be  seen,  as  Mr.  Busk  remarks,  (i  to 
sweep  slowly  and  carefully  over  the  surface  of  the  poly¬ 
zoary,  removing  what  might  be  noxious  to  the  delicate 
inhabitants  of  the  cells  when  their  tentacula  are  pro¬ 
truded.  The  avicularia,  like  the  vibracula,  probably 
seive  for  defence,  but  they  also  catch  and  kill  small  living 
animals,  which,  it  is  believed,  are  afterward  swept  by  the 
currents  within  reach  of  the  tentacula  of  the  zooids.  Some 
species  are  provided  with  avicularia  and  vibracula,  some 
with  avicularia  alone  and  a  few  with  vibracula  alone. 

It  is  not  easy  to  imagine  two  objects  more  widely  dif¬ 
ferent  in  appearance  than  a  bristle  or  vibraculum,  and  an 
avicularium  like  the  head  of  a  bird;  vet  they  are  almost 
certainly  homologous  and  have  been  developed  from  the 
same  common  source,  namely  a  zooid  with  its  cell.  Hence, 
we  can  understand  how  it  is  that  these  organs  graduate  in 
some  cases,  as  I  am  informed  by  Mr.  Busk,  into  each 
other.  .  Thus,  with  the  avicularia  of  several  species  of 
Lepralia,  the  movable  mandible  is  so  much  produced  and 
is  so  like  a  bristle  that  the  presence  of  the  upper  or  fixed 
beak  alone  serves  to  determine  its  avicularian  nature.  The 


230 


MISCELLANEOUS  OBJECTIONS  TO  TEE 


vibracula  may  have  been  directly  developed  from  the  lips 
of  the  cells,  without  having  passed  through  the  avicularian 
stage;  but  it  seems  more  probable  that  they  have  passed 
through  this  stage,  as  during  the  early  stages  of  the  trans¬ 
formation,  the  other  parts  of  the  cell,  with  the  included 
zooid,  could  hardly  have  disappeared  at  once.  In  many 
cases  the  vibracula  have  a  grooved  support  at  the  base, 
which  seems  to  represent  the  fixed  beak;  though  this  sup¬ 
port  in  some  species  is  quite  absent.  This  view  of  the  de¬ 
velopment  of  the  vibracula,  if  trustworthy,  is  interesting; 
for  supposing  that  all  the  species  provided  with  avicularia 
had  become  extinct,  no  one  with  the  most  vivid  imagina¬ 
tion  would  ever  have  thought  that  the  vibracula  had  orig¬ 
inally  existed  as  part  of  an  organ,  resembling  a  bird's  head, 
or  an  irregular  box  or  hood.  It  is  interesting  to  see  two 
such  widely  different  organs  developed  from  a  common 
origin;  and  as  the  movable  lip  of  the  cell  serves  as  a  protec¬ 
tion  to  the  zooid,  there  is  no  difficulty  in  believing  that  all 
the  gradations,  by  which  the  lip  became  converted  first  into 
the  lower  mandible  of  an  avicularium,  and  then  into  an 
elongated  bristle,  likewise  served  as  a  protection  in  different 
ways  and  under  different  circumstances. 

In  the  vegetable  kingdom  Mr.  Mivart  only  alludes  to  two 
cases,  namely  the  structure  of  the  flowers  of  orchids,  and 
the  movements  of  climbing  plants.  With  respect  to  the 
former,  he  says:  “  The  explanation  of  their  origin  is  deemed 
thoroughly  unsatisfactory — utterly  insufficient  to  explain 
the  incipient,  infinitesimal  beginnings  of  structures  which 
are  of  utility  only  when  they  are  considerably  developed." 
As  I  have  fully  treated  this  subject  in  another  work,  I  will 
here  give  only  a  few  details  on  one  alone  of  the  most  strik¬ 
ing  peculiarities  of  the  flowers  of  orchids,  namely,  their  pol- 
linia.  A  pollinium,  when  highly  developed,  consists  of  a 
mass  of  pollen -grains,  affixed  to  an  elastic  foot-stalk  or 
caudicle,  and  this  to  a  little  mass  of  extremely  viscid 
matter.  The  pollinia  are  by  this  means  transported  by  in¬ 
sects  from  one  flower  to  the  stigma  of  another.  In  some 
orchids  there  is  no  caudicle  to  the  pollen-masses,  and  the 
grains  are  merely  tied  together  by  fine  threads;  but  as  these 
are  not  confined  to  orchids,  they  need  not  here  be  consid¬ 
ered;  yet  I  may  mention  that  at  the  base  of  the  orchid*- 


THEORY  OF  NATURAL  SELECTION. 


231 


ceous  series,  in  Cypripedium,  we  can  see  how  the  threads 
were  probably  first  developed.  In  other  orchids  the 
threads  cohere  at  one  end  of  the  pollen-masses;  and  this 
forms  the  first  or  nascent  trace  of  a  caudicle.  That  this  is 
the  origin  of  the  caudicle,  even  when  of  considerable 
length  and  highly  developed,  we  have  good  evidence  in  the 
aborted  pollen-grains  which  can  sometimes  be  detected  em= 
bedded  within  the  central  and  solid  parts. 

With  respect  to  the  second  chief  peculiarity,  namely,  the 
little  mass  of  viscid  matter  attached  to  the  end  of  the  cau¬ 
dicle,  a  long  series  of  gradations  can  be  specified,  each  of 
plain  service  to  the  plant.  In  most  flowers  belonging  to 
other  orders  the  stigma  secretes  a  little  viscid  matter.  Now, 
in  certain  orchids  similar  viscid  matter  is  secreted,  but  in 
much  larger  quantities  by  one  alone  of  the  three  stigmas; 
and  this  stigma,  perhaps  in  consequence  of  the  copious 
secretion,  is  rendered  sterile.  When  an  insect  visits  a 
flower  of  this  kind,  it  rubs  off  some  of  the  viscid  matter, 
and  thus  at  the  same  time  drags  away  some  of  the 
pollen-grains.  From  this  simple  condition,  which  differs 
but  little  from  that  of  a  multitude  of  common 
flowers,  there  are  endless  gradations — to  species  in  which 
the  pollen-mass  terminates  in  a  very  short,  free  cau¬ 
dicle — to  others  in  which  the  caudicle  becomes  firmly  at¬ 
tached  to  the  viscid  matter,  with  the  sterile  stigma  itself 
much  modified.  In  this  latter  case  we  have  a  pollinium 
in  its  most  highly  developed  and  perfect  condition.  He 
who  will  carefully  examine  the  flowers  of  orchids  for 
himself  will  not  deny  the  existence  of  the  above  series  of 
gradations — from  a  mass  of  pollen-grains  merely  tied 
together  by  threads,  with  the  stigma  differing  but  little 
from  that  of  the  ordinary  flowers,  to  a  highly  complex 
pollinium,  admirably  adapted  for  transportal  by  insects; 
nor  will  he  deny  that  all  the  gradations  in  the  several 
species  are  admirably  adapted  in  relation  to  the  general 
structure  of  each  flower  for  its  fertilization  by  different 
insects.  In  this,  and  in  almost  every  other  case,  the  in¬ 
quiry  may  be  pushed  further  backward;  and  it  may  be 
asked  how  did  the  stigma  of  an  ordinary  flower  become 
viscid,  but  as  we  do  not  know  the  full  history  of  any  one 
group  of  beings,  it  is  as  useless  to  ask,  as  it  is  hopeless  to 
attempt  answering*  such  auestions.> 


232  MISCELLANEOUS  OBJECTIONS  TO  THE 


We  will  now  turn  to  climbing  plants.  These  can  be  ar¬ 
ranged  in  a  long  series,  from  those  which  simply  twine 
round  a  support,  to  those  which  I  have  called  leaf-climbers, 
and  to  those  provided  with  tendrils.  In  these  two  latter 
classes  the  stems  have  generally,  but  not  always,  lost  the 
power  of  twining,  though  they  retain  the  power  of  revolv¬ 
ing,  which  the  tendrils  likewise  possess.  The  gradations 
from  leaf-climbers  to  tendril  bearers  are  wonderfully  close, 
and  certain  plants  may  be  differently  placed  in  either 
class.  But  in  ascending  the  series  from  simple  twiners  to 
leaf-climbers,  an  important  quality  is  added,  namely  sen¬ 
sitiveness  to  a  touch,  by  which  means  the  foot-stalks  of  the 
leaves  or  flowers,  or  these  modified  and  converted  into  ten¬ 
drils,  are  excited  to  bend  round  and  clasp  the  touching 
object.  He  who  will  read  my  memoir  on  these  plants  will, 
I  think,  admit  that  all  the  many  gradations  in  function 
and  structure  between  simple  twiners  and  tendril-bearers 
are  in  each  case  beneficial  in  a  high  degree  to  the  species. 
Tor  instance,  it  is  clearly  a  great  advantage  to  a  twining 
plant  to  become  a  leaf-climber;  and  it  is  probable  that 
every  twiner  which  possessed  leaves  with  long  foot-stalks 
would  have  been  developed  into  a  leaf-climber,  if  the  foot¬ 
stalks  had  possessed  in  any  slight  degree  the  requisite  sen¬ 
sitiveness  to  a  touch. 

As  twining  is  the  simplest  means  of  ascending  a  support, 
and  forms  the  basis  of  our  series,  it  may  naturally  be  asked 
how  did  plants  acquire  this  power  in  an  incipient  degree, 
afterward  to  be  improved  and  increased  through  natural 
selection..  The  power  of  twining  depends,  firstly,  on  the 
stems  while  young  being  extremely  flexible  (but" this  is  a 
character  common  to  many  plants  which  are  not  climbers)  ; 
and,  secondly,  on  their  continually  bending  to  all  points  of 
the  compass,  one  after  the  other  in  succession,  in  the  same 
order.  By  this  movement  the  stems  are  inclined  to  all 
sides,  and  are  made  to  move  round  and  round.  As  soon 
as  the  lower  part  of  a  stem  strikes  against  any  object  and 
is  stopped,  the  upper  part  still  goes  on  bending  and  revolv¬ 
ing,  and  thus  necessarily  twines  round  and  up  the  support. 
The  revolving  movement  ceases  after  the  early  growth  of 
each  shoot.  As  in  many  widely  separated  families  of 
plants,  single  species  and  single  genera  possess  the  power 
of  revolving,  and  have  thug  become  twiners,  they  must  have 


THEORY  OF  NATURAL  SELECTION 


233 


independently  acquired  it,  and  cannot  have  inherited  it  from 
a  common  proge^ntor.  Hence,  I  was  led  to  predict  tha 
,  nie  S  ^!lt  1ten/en?y  to  a  movement  of  this*  kind  would 

JJT^0  b/i  fr<?1?  uncomnion  with  plants  which  did 
t  climb,  and  that  this  had  afforded  the  basis  for  natural 

diction n/knp°rk  f°n  Td  imP.rove-  When  I  made  this  pre- 
J.ction,  I  knew  of  only  one  imperfect  case,  namelv  of  the 

young  flower-peduncles  of  a  Maurandia  which  revolted 

lrrf?ularfy,  like  the  stems  of  twining  pknts 

"?.aklng  any  use  of  this  habit.  Soon  afterward 

fnfof  a  Dimmer'6?  ^  S1?  -terns  of  an  llfsma 
sena-nted  in  Plants  which  do  not  climb  and  are  widely 
irret?]^^  ^  sysfcem— revolved  plainly,  though 

thaTfPii7 ’  and  he.,s^ates  that  hQ  has  reason  to  suspect 
that  this  occurs  with  some  other  plants.  These  slight 

movements  appear  to  be  of  no  service  to  the  plants  in  ques 

t  on;  anyhow,  they  are  not  of  the  least  use  in  the  wav  of 

c  lmbmg,  which  is  the  point  that  concerns  us.  Neverthe 

flelibV  CaodSe*f  4  ^ lf  +t1hestemsof  these  plants  had  been 
flexible  and  if  under  the  conditions  to  which  they  are  ex 

posea  it  had  profited  them  to  ascend  to  a  height  idien  the 

rr0llinS  m>ght  havVbeen 
mcieasea  and  utilized  through  natural  selection,  until  thev 

h  Wnh°reLCeTetnilUlt0  we.11;develoPed  twining  species7 
i  respect  to  the  sensitiveness  of  the  foot-stalks 

of  the  leaves  and  flowers,  and  of  tendrils,  nearlv  the 

same  remarks  are  applicable  as  in  the  case  of  the  revolv- 

g  movements  of  twining  plants.  As  a  vast  number  of 

whh  this ' MndTf  sp  Wv6ly  distinot  grouPs,  are  endowed 
witn  tins  kind  of  sensitiveness,  it  ought  to  be  found  in 

com?0ceflmbeTsdltlTh'm plants  which  have  not  be¬ 
come  cumbers.  This  is  the  case:  I  observed  tint  tha 

young  flower-peduncles  of  the  above  Maurandia  curbed 

themselves  a  little  toward  the  side  which Tas  touched 

Md  tblf0  rntl  f,eyeral  sPecies  of  Oxalis  that  the  leaves 

hot  sun  wlmn  H  3  kS  moved’ 1 especially  after  exposure  to  a 
TT  s  ,n>  when  they  were  gently  and  repeatedly  touched  or 

when  the  plant  was  shaken,  f  repeated  these  obsefvati’ons 

some  fif  tnher  ®?ecies  of  0xalis  with  the  same  result-  in 
in  fthlh!m  th?  move“ent  was  distinct,  but  was  best 
I??"  the  y°n.nS  leayesi  ™  others  it  was  extremely  slight 
It  is  a  more  important  fact  that  according  to  the  high 


234  MISCELLANEOUS  OBJECTIONS  TO  THE 

authority  of  Hofmeister,  the  young  shoots  and  leaves  of 
all  plants  move  after  being  shaken;  and  with  climbing 
plants  it  is,  as  we  know,  only  during  the  early  stages  of 
growth  that  the  foot-stalks  and  tendrils  are  sensitive. 

it  is  scarcely  possible  that  the  above  slight  movements, 
due  to  a  touch  or  shake,  in  the  young  and  growing  organs 
of  plants,  can  be  of  any  functional  importance  to  them. 
But  plants  possess,  in  obedience  to  various  stimuli,  poweis 
of  movement,  which  are  of  manifest  importance  to  them, 
for  instance,  toward  and  more  rarely  from  the  hgh 
in  opposition  to,  and  more  rarely  m  tne  direction  ot,  the 
attraction  of  gravity.  When  the  nerves  and  muscles  of  an 
animal  are  excited  by  galvanism  or  by  the  absorption  of 
strychnine,  the  consequent  movements  may  be  called  an 
incidental^ result,  for  the  nerves  and  muscles  have  not  been 
rendered  specially  sensitive  to  these  stimuli,  oo  aw  1 
plants  it  i  ppears  that,  from  having  the  power  of  movement 
in  obedience  to  certain  stimuli,  they  are  excited  man  in¬ 
cidental  manner  by  a  touch,  or  by  being  shaken,  lienee 
there  is  no  great  difficulty  in  admitting  that  in  the  case  ot 
leaf-climbers  and  tendril-bearers,  it  is  this  tendency  which 
has  been  taken  advantage  of  and  increased  through  natuial 
selection.  It  is,  however,  probable,  from  reasons  which  1 
have  assigned  in  my  memoir,  that  this  will  have  occurred 
only  with  plants  which  had  already,  acquired  the  power 
of  revolving,  and  had  thus  become  twiners. 

I  have  already  endeavored  to  explain  how  plants  became 
twiners,  namely,  by  the  increase  of  a  tendency  to  slight 
and  irregular  revolving  movements,  which  were  at  first  of 
no  use  to  them;  this  movement,  as  well  as  that  due  to  a 
touch  or  shake,  being  the  incidental  result  of  the  power  ot 
moving,  gained  for  other  and  beneficial  purposes.  W  nether, 
during0 the  gradual  development  of  climbing  plants,  nat¬ 
ural  selection  has  been  aided  by  the  inherited  effects  of 
use,  I  will  not  pretend  to  decide;  but  we  know  that  certain 
periodical  movements,  for  instance  the  so-called  sleep  of 
plants,  are  governed  by  habit. 

I  have  now  considered  enough,  perhaps  more  than 
enough,  of  the  cases,  selected  with  care  by  a  skillful  natu¬ 
ralist,  to  prove  that  natural  selection  is  incompetent  to  ac¬ 
count  for  the  incipient  stages  of  useful  structures;  and 


235 


THEOR  T  OF  NA  TURAL  SEL EGT10 W. 

have  shown,  as  1  hope,  that  there  is  no  great  difficulty  on 
tins  bead.  A  good  opportunity  has  thus  been  afforded  for 
a  on  gradations  of  structure,  often  associ¬ 
ated  with  strange  functions — an  important  subject,  which 
tre.atedTat  sufficient  length  in  the  former  editions 
o,  i,his  work.  I  will  now  briefly  recapitulate  the  foregoing 
^ases. 

With  the  giraffe,  the  continued  preservation  of  the  indi¬ 
viduals  of  some  extinct  high-reaching  ruminant,  which  had 
the  longest  necks,  legs,  etc.,  and  could  browse  a  little 
above  the  average  height,  and  the  continued  destruction  of 
those  which  could  not  browse  so  high,  would  have  sufficed 
ioi  the  production  of  this  remarkable  quadruped:  but  the 
prolonged  use  of  all  the  parts,  together  with  inheritance, 
will  have  aided  in  an  important  manner  in  their  jo-ordina- 
tion.  With  the  many  insects  which  imitate  vt  rious  ob¬ 
jects  there  is  no  improbability  in  the  belief  that  an  acci¬ 
dental  resemblance  to  some  common  object  was  in  each  case 
the  foundation  for  the  work  of  natural  selection,  since  per¬ 
fected  through  the  occasional  preservation  of  slight  variations 
which  made  the  resemblance  at  all  closer;  and  this  will  have 
been  carried  on  as  long  as  the  insect  continued  to  vary, 
and  as  long  as  a  more  and  more  perfect  resemblance  led  to 
\ts  escape  from  sharp-sighted  enemies.  In  certain  species 
of  whales  there  is  a  tendency  to  the  formation  of  irregular 
httle  points  of  horn  on  the  palate;  and  it  seems  to  be  quite 
within  the  scope  of  natural  selection  to  preserve  all  favor¬ 
able  variations,  until  the  points  were  converted,  first  into 
lamellated  knobs  or  teeth,  like  those  on  the  beak  of  a 
goose— then  into  short  lamellae,  like  those  of  the  domestic 
clucks— and  then  into  lamellae,  as  perfect  as  those  of  the 
shoveller-duck— and  finally  into  the  gigantic  plates  of 
baleen,  as  m  the  mouth  of  the  Greenland  whale.  In  the 
iamily  of  the  ducks,  the  lamellae  are  first  used  as  teeth 
en  partly  as  teeth  and  partly  as  a  sifting  apparatus,  and 
at  last  almost  exclusively  for  this  latter  purpose. 

With  such  structures  as  the  above  lamellae  of  horn  or 
whalebone,  habit  or  use  can  have  done  little  or  nothing  as 
tar  as  we  can  judge,  toward  their  development.  On  the 
other  hand,  the  transportal  of  the  lower  eye  of  a  fiat- 
hsh  to  the  upper  side  of  the  head,  and  the  formation  of  a 
prehensile  tail,  may  be  attributed  almost  wholly  to  con- 


236  MISCELLANEOUS  OBJECTIONS  TO  THE 

tinued  use,  together  with  inheritance.  With  respect  to 
the  mammae  of  the  higher  animals,  the  most  probable  con¬ 
jecture  is  that  primordially  the  cutaneous  glands  over 
the  whole  surface  of  a  marsupial  sack  secreted  a  nutritious 
fluid;  and  that  these  glands  were  improved  in  function 
through  natural  selection,  and  concentrated  into  a  confined 
area,  in  which  case  they  would  have  formed  a  mamma. 
There  is  no  more  difficulty  in  understanding  how  the 
branched  spines  of  some  ancient  Echinoderm,  which 
served  as  a  defence,  became  developed  through  natural 
selection  into  tridactyle  pedicellariae,  than  in  understand¬ 
ing  the  development  of  the  pincers  of  crustaceans,  through 
slight,  serviceable  modifications  in  the  ultimate  and  pe¬ 
nultimate  segments  of  a  limb,  which  was  at  first  used  solely 
for  locomotion.  In  the  avicularia  and  vibracula  of  the 
Polyzoa  we  have  organs  widely  different  in  appearance 
developed  from  the  same  source;  and  with  the  vibracula 
we  can  understand  how  the  successive  gradations  might 
have  been  of  service.  With  the  pollinia  of  orchids,  the 
threads  which  originally  served  to  tie  together  the  pollen- 
grains,  can  be  traced  cohering  into  caudicles;  and  the  steps 
can  likewise  be  followed  by  which  viscid  matter,  such  as 
that  secreted  by  the  stigmas  of  ordinary  flowers,  and  still 
subserving  nearly  but  not  quite  the  same  purpose,  became 
attached  to  the  free  ends  of  the  caudicles — all  these  grada¬ 
tions  being  of  manifest  benefit  to  the  plants  in  question. 
With  respect  to  climbing  plants,  I  ne*d  not  repeat  what 
has  been  so  lately  said. 

It  has  often  been  asked,  if  natural  selection  be  so  potent, 
why  has  not  this  or  that  structure  been  gained  by  certain 
species,  to  which  it  would  apparently  have  been  advan¬ 
tageous?  But  it  is  unreasonable  to  expect  a  precise  answer 
to  such  questions,  considering  our  ignorance  of  the  past 
history  of  each  species,  and  of  the  conditions  which  at  the 
present  day  determine  its  numbers  and  range.  In  most 
cases  only  general  reasons,  but  in  some  few  cases  special 
reasons,  can  be  assigned.  Thus  to  adapt  a  species  to  new 
habits  of  life,  many  co-ordinated  modifications  are  almost 
indispensable,  and  it  may  often  have  happened  that  the 
requisite  parts  did  not  vary  in  the  right  manner  or  to  the 
right  degree.  Many  species  must  have  been  prevented 
from  increasing  in  numbers  through  destructive  agencies, 


THEOR  T  OF  JSTA  TURAL  SELECTIO 2T.  23  7 

stood  in  no  relation  to  certain  structures,  which  we 
imagine  would  have  been  gained  through  natural  selection 
from  appearing  to  us  advantageous  to  the  species  In  this 
case,  as  the  struggle  for  life  did  not  depend™  schsHuc 
ures  they  could  not  have  been  acquired  through  natural 
selection  In  many  cases  complex  and  long-enduring  con¬ 
i’  10inS’  ofte,n  °f  ia  peculiar  nature,  are  necessary  for  the 
development  of  a  structure;  and  the  requisite  conditions 
may  seldom  have  concurred.  The  belief  that  any  given 

we  think,  often  erroneously,  would  Shave 
been  beneficial  to  a  species,  would  have  been" gained  under 
all  circumstances  through  natural  selection,  if  opposed  to 
what  we  can  understand  of  its  manner  of  action.  Mr 

somethin^8  bnt  ^  na.tural  selection  has  effected 
something,  but  he  considers  it  as  “demonstrably  insuf- 

ftslefaencfaCTntfr%thephen°menawhich  1  exPlain  by 
its  agency.  His  chief  arguments  have  now  been  con¬ 
sidered,  and  the  others  will  hereafter  be  considered.  They 

Hnn“  t0un‘te  f0  par,takne  little  of  the  character  of  demonstraf 
tion,  and  to  have  little  weight  in  comparison  with  those  in 

favoi  of  the  power  of  natural  selection,  aided  by  the  other 
agencies  often  specified.  Iam  bound  to  add,  that  some  of 

vaLed^ a“d  arguments  here  used  by  me,  have  been  ad- 
10‘  th°  same  purpose  m  au  able  article  lately  pub¬ 
lished  in  the  ‘Medico-Chirurgical  Review.”  P 

At  the  present  day  almost  all  naturalists  admit  evolution 

throuVh°“f  l  r-r  iVai,t  Relieves  species  change 

Hough  an  internal  force  or  tendency,”  about  which  "it 
is  not  pretended  that  anything  is  known.  That  species 
have  a  capacity  for  change  will  be  admitted  by  all  evolu¬ 
tionists;  but  there  is  no  need,  as  it  seems  to  me,  to  invoke 

bdiiv  T?ai  /,0rCe  ^ey,ond  the  tendency  to  ordinary  varia¬ 
bility  which  through  the  aid  of  selection,  by  man  has  given 

me  to  many  well-adapted  domestic  races,  and  wh?ch 

gHe1  nt  T  a'd  ,°f  ,natural  election,  would  equally  well 
give  rise  by  graduated  steps  to  natural  races  or  species 

ihe  final  result  will  generally  have  been,  as  already  exl 

plained,  an  advance,  but  m  some  few  cases  a  retrogression 
in  organization.  5 

Mr.  Mivart  is  further  inclined  to  believe  and  some 
naturalists  agree  with  him,  that  new  species  manifest 
themselves  “  with  suddenness  and  by  modifications  appear 


238  MISCELLANEOUS  OBJECTIONS  TO  THE 

in o-  at  once.”  For  instance,  he  supposes  that  the  differ¬ 
ences  between  the  extinct  three-toed  Hippanon  and  the 
horse  arose  suddenly.  He  thinks  it  difficult  to  believe  that 
the  wing  of  a  bird  “was  developed  m  any  other  way  than 
by  a  comparatively  sudden  modification  of  a  marked  and 
important  kind  and  apparently  he  would  extend  the 
same  view  to  the  wings  of  bats  and  pterodactyles.  I  Ins 
conclusion,  which  implies  great  breaks  or  discontinuity  in 
the  series,  appears  to  me  improbable  m  the  highest  degree. 

Every  one  who  believes  in  slow  and  gradual  evolution, 
will  of  course  admit  that  specific  changes  may  have  been 
as  abrupt  and  as  great  as  any  single  variation  which  we 
meet  with  under  nature,  or  even  under  domestication. 
But  as  species  are  more  variable  when  domesticated  or  cul¬ 
tivated  than  under  their  natural  conditions,  it  is  not  piob- 
able  that  such  great  and  abrupt  variations  have  often 
occurred  under  nature,  as  are  known  occasionally  to  anso 
under  domestication.  Of  these  latter  variations  several 
may  be  attributed  to  reversion;  and  the  character  which 
thus  reappear  were,  it  is  probable,  in  many  cases  ar  hist 
rained  in  a  gradual  manner.  A  still  greater  number  must 
be  called  monstrosities,  such  as  six-fingered  men,  porcupine 
men,  Ancon  sheep,  Niata  cattle,  etc.;  and  as  they  are 
widely  different  in  character  from  natural  species,  they 
throw  very  little  light  on  our  subject.  Excluding  such 
cases  of  abrupt  variations,  the  few  wlucn  remain  would  at 
best  constitute,  if  found  in  a  state  of  natuie,  doubtful 
species,  closely  related  to  their  parental  types.  . 

My  reasons  for  doubting  whether  natural  species  hare 
changed  as  abruptly  as  have  occasionally  domestic  races, 
and  for  entirely  disbelieving  that  they  have  changed  in  the 
wonderful  manner  indicated  by  Mr.  Mivart,  are  as  follows. 
According  to  our  experience,  abrupt  and  strongly  marked 
variations  occur  in  our  domesticated  productions,  sing  y 
and  at  rather  long  intervals  of  time.  If  such  occurrec 
under  nature,  they  would  be  liable,  as  formerly  explained, 
to  be  lost  by  accidental  causes  of  destruction  and  by  subse¬ 
quent  intercrossing;  and  so  it  is  known  to  be  under  o- 
mestieation,  unless  abrupt  variations  of  this  kind  are  spec¬ 
ially  preserved  and  separated  by  the  care  of  man.  Hence, 
in  order  that  a  new  species  should  suddenly  appear  m  the 
manner  supposed  by  Mr.  Mivart,  it  is  almost  necessary  to 


THEOR  T  OF  NA  TURAL  SEL  ECTION. 


239 


believe,  in  opposition  to  all  analogy,  that  several  wonder¬ 
fully  changed  individuals  appeared  simultaneously  within 
the  same  district.  This  difficulty,  as  in  the  case  of  uncon¬ 
scious  selection  by  man,  isavoided  on  the  theory  of  gradual 
evolution  through  the  preservation  of  a  large  number  of 
individuals,  which  varied  more  of  less  in  any  favorable 
dnection,  and  of  the  destruction  of  a  large  number  which 
varied  in  an  opposite  manner. 

That  many  species  have  been  evolved  in  an  extremelv 
gradual  manner,  there  can  hardly  be  a  doubt.  The  species 
and  even  the  genera  of  many  large  natural  families  are  so 
closely  allied  together  that  it  is  difficult  to  distinguish  not 
a  few  of  them  On  every  continent,  in  proceeding  from 
north  to  south,  from  lowland  to  upland,  etc.,  we  meet  with 
a  host  of  closely  related  or  representative  species;  as  we 
likewise  do  on  certain  distinct  continents,  which  we  have 
reason  to  believe  were  formerly  connected.  But  in  making 
these  and  the  following  remarks,  I  am  compelled  to  allude  tS 
subjects  hereafter  to  be  discussed.  Look  at  the  many  out- 
-  round  a  continent,  and  see  how  many  of  their 

inhabitants  can  be  raised  only  to  the  rank  of  doubtful 
species.  So  it  is  if  we  look  to  past  times,  and  compare  the 
species  which  have  just  passed  away  with  those  still  living 

•Vlti.11^t^e-Sa??e  ar^as;  or  if  we  compare  the  fossil  species 
imbedded  in  the  sub-stages  of  the  same  geological  forma- 

tmn.  It  is  indeed  manifest  that  multitudes  of  species 
are  related  in  the  closest  manner  to  other  species  that  still 
exist  or  haVe  lately  existed;  and  it  will  hardly  be  main¬ 
tained  that  such  species  have  been  developed  in  an  abrupt 
or  sudden  manner.  Nor  should  it  be  forgotten,  when  we 
look  to  the  special  parts  of  allied  species,  instead  of  to  dis¬ 
tinct  species,  that  numerous  and  wonderfully  fine  grada¬ 
tions  can  be  traced,  connecting  together  widely  different 

Many  large  groups  of  facts  are  intelligible  only  on  the 
principle  that  species  have  been  evolved  by  very  small  steps. 

or  instance,  the  fact  that  the  species  included  in  the 
larger  genera  are  more  closely  related  to  each  other  and 
present  a  greater  number  of  varieties  than  do  the  species 

_  i m  ...  _  a  e  also  grouped  in 

little  clusters,  like  varieties  round  species;  and  they  present 

other  analogies  with  varieties,  as  was  shown  in  our  second 


240 


MISCELLANEOUS  OBJECTIONS  TO  TEE 

chapter.  On  this  same  principle  we  can  understand  how 
it  is  that  specific  characters  are  more  variable  than  generic 
characters;  and  how  the  parts  which  are  developed  m  an 
extraordinary  degree  or  manner  are  more  variable  than 
other  parts  of  the  same  species.  Many  analogous  facts,  all 
pointing  in  the  same  direction,  could  be  added. 

Although  very  many  species  have  almost  certainly  been 
produced  by  steps  not  greater  than  those  separating  line 
varieties;  yet  it  may  be  maintained  that  some  have  been 
developed  in  a  different  and  abrupt  manner.  Such  an 
admission,  however,  ought  not  to  be  made  without  stiong 
evidence  being  assigned.  The  vague  and  in  some  respects 
false  analogies,  as  they  have  been  shown  to  be  by  Mr. 
Chauncey  Wright,  which  have  been  advanced  m  favor  of 
this  view,  such  as  the  sudden  crystallization  of  inoiganic 
substances,  or  the  falling  of  a  facetted  spheroid  from  one 
facet  to  another,  hardly  deserve  consideration.  One  class 
of  facts,  however,  namely,  the  sudden  appearance  of  new 
and  distinct  forms  of  life  in  our  geological  formations  sup¬ 
ports  at  first  sight  the  belief  in  abrupt  development.  But 
the  value  of  this  evidence  depends  entirely  on  the  perfec¬ 
tion  of  the  geological  record,  in  relation  to  periods  remote 
in  the  history  of  the  world.  If  the  record  is  as  frag¬ 
mentary  as  many  geologists  strenuously  assert,  theie  is 
nothing  strange  in  new  forms  appearing  as  if  suddenly 
developed. 

Unless  we  admit  transformations  as  prodigious  as  tnose 
advocated  by  Mr.  Mivart,  such  as  the  sudden  development 
of  the  wings  of  birds  or  bats,  or  the  sudden  conversion  of 
a  ITipparion  into  a  horse,  hardly  any  light  is  thrown  by  the 
oelief  in  abrupt  modifications  on  the  deficiency  of  connect¬ 
ing  links  in  our  geological  formations.  But  against  the 
belief  in  such  abrupt  changes,  embryology  enters  a  strong 
protest.  It  is  notorious  that  the  wings  of  birds  and  bats, 
and  the  legs  of  horses  or  other  quadrupeds,  are  undis- 
tinguishable  at  an  early  embryonic  period,  and  that  they 
become  differentiated  by  insensibly  fine  steps.  Embryo- 
logical  resemblances  of  ail  kinds  can  be  accounted  for,.  as 
we  shall  hereafter  see,  by  the  progenitors  of^  our  existing 
species  having  varied  after  early  youth,  and  having  trans¬ 
mitted  their  newly-acquired  characters  to  their  offspring, 
at  a  corresponding  age.  The  embryo  is  thus  left  almost 


THEORY  OF  NATURAL  SELECTION. 


241 

unaffected,  and  serves  as  a  record  of  the  past  condition  of 
the  species.  Hence  it  is  that  existing  species  during  the 
early  stages  of  their  development  so  often  resemble  ancient 
and  extinct  forms  belonging  to  the  same  class.  On  this 
view  of  the  meaning  of  _  embryological  resemblances,  and 
a  v  view,  it  is  incredible  that  an  animal 
should  have  undergone  such  momentous  and  abrupt  trans¬ 
formations  as  those  above  indicated,  and  yet  should  not 
bear  even  a  trace  in  its  embryonic  condition  of  any  sudden 
modification,  every  detail  in  its  structure  being  developed 
by  insensibly  fine  steps. 

He  who  believes  that  some  ancient  form  was  transformed 
suddenly  through  an  internal  force  or  tendency  into,  for 
instance,  one  furnished  with  wings,  will  be  almost  com¬ 
pelled  to  assume,  in  opposition  to  all  analogy,  that  many 
individuals  varied  simultaneously.  It  cannot  be  denied 
that  such  abrupt  and  great  changes  of  structure  are  widely 
different  from  those  which  most  species  apparently  have 
undergone.  He  will  further  be  compelled  to  believe  that 
many  structures  beautifully  adapted  to  all  the  other  parts 
of  the  same  creature  and  to  the  surrounding  conditions, 
have  been  suddenly  produced;  and  of  such  complex  and 
wonderful  co-adaptations,  he  will  not  be  able  to  assign  a 
shadow  of  an  explanation.  He  will  be  forced  to  admit 
that  these  great  and  sudden  transformations  have  left  no 
trace  of  their  action  on  the  embryo.  To  admit  all  this  is, 
as  it  seems  to  me,  to  enter  into  the  realms  o£  miracle,  and 
to  leave  those  of  science. 


242 


INSTINCT. 


CHAPTER  Yin. 

INSTINCT. 

Instincts  comparable  with  habits,  but  different  in  their  origin- 
instincts  graduated  —  Aphides  and  ants  —  Instincts  variable — 
Domestic  instincts,  their  origin — Natural  instincts  of  the  cuckoo, 
molothrus,  ostrich  and  parasitic  bees — Slave-making  ants  — 
Hive-bee,  its  cell-making  instinct  —  Changes  of  instinct  and 
structure  not  necessarily  simultaneous — Difficulties  of  the  theory 
of  the  Natural  Selection  of  instincts— Neuter  or  sterile  insects— 
Summary. 

Many  instincts  are  so  wonderful  that  their  development 
will  probably  appear  to  the  reader  a  difficulty  sufficient  to 
overthrow  my  whole  theory.  I  may  here  premise,  that  I 
have  nothing  to*do  with  the  origin  of  the  mental  powers, 
any  more  than  I  have  with  that  of  life  itself.  We  are  con¬ 
cerned  only  with  the  diversities  of  instinct  and  of  the 
other  mental  faculties  in  animals  of  the  same  class. 

I  will  not  attempt  any  definition  of  instinct.  It  would 
be  easy  to  show  that  several  distinct  mental  actions  are 
commonly  embraced  by  this  term;  but  every  one  under¬ 
stands  what  is  meant,  when  it  is  said  that  instinct  impels 
the  cuckoo  to  migrate  and  to  [lay  her  eggs  in  other  birds’ 
nests.  An  action,  which  we  ourselves  require  experience 
to  enable  us  to  perform,  when  performed  by  an  animal, 
more  especially  by  a  very  young  one,  without  experience, 
and  when  performed  by  many  individuals  in  the  same  way, 
without  their  knowing  for  what  purpose  it  is  performed,  is 
usually  said  to  be  instinctive.  But  I  could  show  that  none 
of  these  characters  are  universal.  A  little  dose  of  judg¬ 
ment  or  reason,  as  Pierre  Huber  expresses  it,  often  comes 
into  play,  even  with  animals  low  in  the  scale  of  nature. . 

Frederick  Cuvier  and  several  of  the  older  metaphysicians 
have  compared  instinct  with  habit.  This  comparison 
gives,  I  think,  an  accurate  notion  of  the  frame  of  mind 


INSTINCT. 


243 

under  which  an  instinctive  action  is  performed,  but  not 
necessarily  of  its  origin.  How  unconsciously  many  habitual 
actions  are  performed,  indeed  not  rarely  in  direct  oppo¬ 
sition  to  our  conscious  will  !  yet  they  may  be  modified  by 
the  will  or  reason.  Habits  easily  become  associated  with 
othei  habits,  with  certain  periods  of  time  and  states  of  the 
body.  When  once  acquired,  they  often  remain  constant 
throughout  life.  Several  other  points  of  resemblance 
between  instincts  and  habits  could  be  pointed  out.  As  in 
repeating  a  well-known  song,  so  in  instincts,  one  action 
follows  another  by  a  sort  of  rhythm*  if  a  person  be  inter¬ 
rupted  m  a  song,  or  in  repeating  anything  by  rote,  he  is 
geneially  foiced  to  go  back  to  recover  the  habitual  train  of 
thought;  so  P.  Huber  found  it  was  with  a  caterpillar, 
which  makes  a  very  complicated  hammock;  for  if  lie  took 
a  caterpillar  which  had  completed  its  hammock  uji  to,  say, 
the  sixth  stage  of  construction,  and  put  it  into  a  hammock 
completed  up  only  to  the  third  stage,  the  caterpillar  simply 
re-performed  the  fourth,  fifth  and  sixth  stages  of  con¬ 
struction.  If,  however,  a  caterpillar  were  taken  out  of  a 
hammock  made  up,  for  instance,  to  the  third  stage,  and 
were  put .  into  one  finished  up  to  the  sixth  stage,  so  that 
much  of  its  work  was  already  done  for  it,  far  from  deriving 
any  benefit  from  this,  it  was  much  embarrassed,  and  in 
order  to  complete  its  hammock,  seemed  forced  to  start 
from  the  third  stage,  where  it  had  left  off,  and  thus  tried 
to  complete  the  already  finished  work. 

If  we  suppose  any  habitual  action  to  become  inherited — 
and  it  can  be  shown  that  this  does  sometimes  happen— 
then  the  resemblance  between  what  originally  was  a  habit 
and  an  instinct  becomes  so  close  as  not  to  be  distinguished 
If  Mozart,  instead  of  playing  the  piano-forte  at  three  years 
old  with  wonderfully  little  practice,  had  played  a  tune  with 
no  practice  at  all,  he  might  truly  be  said  to  have  done  so 
instinctively.  But  it  would  be  a  serious  error  to  suppose 
that  the  greater  number  of  instincts  have  been  acquired  by 
habit  m  one  generation,  and  then  transmitted  by  inherit¬ 
ance  to  succeeding  generations.  It  can  be  clearly  shown 
that  the  most  wonderful  instincts  with  which  we  are 
acquainted,  namely,  those  of  the  hive-bee  and  of  many  ants, 
could  not  possibly  have  been  acquired  by  habit. 

It  will  be  universally  admitted  that  instincts  are  as  im- 


INSTINCT. 


244 

portant  as  corporeal  structures  for  the  welfare  of  each 
species,  under  its  present  conditions  of  life.  Under 
changed  conditions  of  life,  it  is  at  least  possible  that  slight 
modifications  of  instinct  might  be  profitable  to  a  species; 
and  if  it  can  be  shown  that  instincts  do  vary  ever  so  little, 
then  I  can  see  no  difficulty  in  natural  selection  preserving 
and  continually  accumulating  variations  of  instinct  to  any 
extent  that  was  profitable.  It  is  thus,  as  I  believe,  that  all 
the  most  complex  and  wonderful  instincts  have  originated. 
As  modifications  of  corporeal  structure  arise  from,  and  are 
increased  by,  use  or  habit,  and  are  diminished  or  lost  by 
disuse,  so  I  do  not  doubt  it  has  been  with  instincts.  But 
I  believe  that  the  effects  of  habit  are  in  many  cases  of  sub¬ 
ordinate  importance  to  the  effects  of  the  natural  selection 
of  what  may  be  called  spontaneous  variations  of  instincts — 
that  is  of  variations  produced  by  the  same  unknown  causes 
which  produce  slight  deviations  of  bodily  structure. 

No  complex  instinct  can  possibly  be  produced  through 
natural  selection,  except  by  the  slow  and  gradual  accumu¬ 
lation  of  numerous  slight,  yet  profitable,  variations.  Hence, 
as  in  the  case  of  corporeal  structures,  we  ought  to  find  in 
nature,  not  the  actual  transitional  gradations  by  which 
each  complex  instinct  has  been  acquired— for  these  could 
be  found  only  in  the  lineal  ancestors  of  each  species— but 
we  ought  to  find  in  the  collateral  lines  of  descent  some 
evidence  of  such  gradations;  or  we  ought  at  least  to  be 
able  to  show  that  gradations  of  some  kind  are  possible;  and 
this  we  certainly  can  do.  I  have  been  surprised  to  find, 
making  allowance  for  the  instincts  of  animals  having  been 
but  little  observed,  except  in  Europe  and  North  America, 
and  for  no  instinct  being  known  among  extinct  species,  how 
very  generally  gradations,  leading  to  the  most  complex  in¬ 
stincts,  can  be  discovered.  Changes  of  instinct  may  some¬ 
times  be  facilitated  by  the  same  species  having  different  in¬ 
stincts  at  different  periods  of  life,  or  at  different  seasons  of 
the  year,  or  when  placed  under  different  circumstances, 
etc. ;  in  which  case  either  the  one  or  the  other  instinct 
might  be  preserved  by  natural  selection.  And  such  in¬ 
stances  of  diversity  of  instinct  in  the  same  species  can  be 
shown  to  occur  in  nature. 

Again,  as  in  the  case  of  corporeal  structure,  and  con¬ 
formably  to  my  theory,  the  instinct  of  each  species  is  good 


INSTINCT. 


Mb 

for  itself;  but  has  never,  as  far  as  we  can  judge,  been  pro¬ 
duced  for  the  exclusive  good  of  others.  One  of  the  strong¬ 
est  instances  of  an  animal  apparently  performing  an 
action  for  the  sole  good  of  another,  with  which  I  am 
acquainted,  is  that  of  aphides  voluntarily  yielding,  as  was 
first  observed  by  Huber,  their  sweet  excretion  to  ants:  that 
they  do  so  voluntarily,  the  following  facts  show:  I  re¬ 
moved  all  the  ants  from  a  group  of  about  a  dozen  aphides 
on  a  dock-plant,  and  prevented  their  attendance  during 
several  hours.  After  this  interval,  I  felt  sure  that  the 
aphides  would  want  to  excrete.  I  watched  them  for  some 
time  through  a  lens,  but  not  one  excreted;  I  then  tickled 
and  stroked  them  with  a  hair  in  the  same  manner,  as  well 
as  I  could,  as  the  ants  do  with  their  antennas;  but  not 
one  excreted.  Afterward,  I  allowed  an  ant  to  visit  them, 
and  it  immediately  seemed,  by  its  eager  way  of  running 
about  to  be  well  awa^e  what  a  rich  flock  it  had  discovered; 
it  then  begun  to  play  with  its  antennas  on  the  abdomen 
first  of  one  aphis  and  then  of  another;  and  each,  as  soon  as 
it  felt  the  antennas,  immediately  lifted  up  its  abdomen  and 
excreted  a  limped  drop  of  sweet  juice,  which  was  eagerly 
devoured  by  the  ant.  Even  the  quite  young  aphides  be¬ 
haved  in  this  manner,  showing  that  the  action  was  instinc¬ 
tive,  and  not  the  result  of  experience.  It  is  certain,  from 
the  observations  of  Huber,  that  the  aphides  show  no  dis¬ 
like  to  the  ants:  if  the  latter  be  not  present  they  are  at 
last  compelled  to  eject  their  excretion.  But  as  the  excre¬ 
tion  is  extremely  viscid,  it  is  no  doubt  a  convenience  to 
the  aphides  to  have  it  removed;  therefore  probably  they  do 
not  excrete  solely  for  the  good  of  the  ants.  Although 
there  is  no  evidence  that  any  animal  performs  an  action 
for  the  exclusive  good  of  another  species,  yet  each  tries  to 
take  advantage  of  the  instincts  of  others,  as  each  takes 
advantage  of  the  weaker  bodily  structure  of  other 
species.  So  again  certain  instincts  can  not  be  considered  as 
absolutely  perfect;  but  as  details  on  this  and  other  such 
points  are  not  indispensable,  they  may  be  here  passed 
over. 

As  some  degree  of  variation  in  instincts  under  a  state  of 
nature,  and  the  inheritance  of  such  variations,  are  indis¬ 
pensable  for  the  action  of  natural  selection,  as  many 
instances  as  possible  ought  to  be  given;  but  want  of  space 


INSTINCT. 


246 

prevents  me.  I  can  only  assert  that  instincts  certainly  do 

vary _ for  instance,  tlie  migratory  instinct,  both  in  extent 

and.  direction,  and  in  its  total  loss.  So  it  is  with  the  nests 
of  birds,  which  vary  partly  in  dependence  on  the  situations 
chosen,  and  on  the  nature  and  temperature  of  the  country 
inhabited,  but  often  from  causes  wholly  unknown  to  us. 
Audubon  has  given  several  remarkable  cases  of  differences 
in  the  nests  of  the  same  species  in  the  northern  and  south¬ 
ern  United  States.  Why,  it  has  been  asked,  if  instinct  be 
variable,  has  it  not  granted  to  the  bee  “  the  ability  to  use 
some  other  material  when  wax  was  deficients  But  what 
other  natural  material  could  bees  use?  They  will  work,  as 
I  have  seen,  with  wax  hardened  with  vermilion  or  solt- 
ened  with  lard.  Andrew  Knight  observed  that  his  bees, 
instead  of  laboriously  collecting  propolis,  used  a  cement  of 
wax  and  turpentine,  with  which  he  had  coveied  dccoi- 
ticated  trees.  It  has  lately  been  slio^wn  that  bees,  instead 
of  searching  for  pollen,  will  gladly  use  a  very  different 
substance,  namely,  oatmeal.  Fear  of  any  particular  enemy 
is  certainly  an  instinctive  quality,  as  may  be  seen  in  nest¬ 
ling  birds,  though  it  is  strengthened  by  experience,  and  by 
the  sight  of  fear  of  the  same  enemy  in  other  animals.  The 
fear  of  man  is  slowly  acquired,  as  I  have  elsewhere  shown, 
by  the  various  animals  which  inhabit  desert  islands;  and 
we  see  an  instance  of  this  even  in  England,  in  the  greatei 
wildness  of  all  our  large  birds  in  comparison  with  our  small 
birds;  for  the  large  birds  have  been  most  persecuted  by 
man/  We  may  safely  attribute  the  greater  wildness  of  our 
large  birds  to  this  cause;  for  in  uninhabited  islands  large 
birds  are  not  more  fearful  than  small;  and  the  magpie,  so 
wary  in  England,  is  tame  in  Korway,  as  is  the  hooded  ciow 

in  Egypt.  .  .  ,  .  . 

That  the  mental  qualities  of  animals  of  the  same  kind, 
born  in  a  state  of  nature,  vary  much,  could  be  shown  by 
many  facts.  Several  cases  could  also  be  adduced  of  occa¬ 
sional  and  strange  habits  in  wild  animals,  which,  if  advan¬ 
tageous  to  the  species,  might  have  given  rise,  through 
natural  selection,  to  new  instincts.  But  I  am  well  aware 
that  these  general  statements,  without  the  facts  in  detail, 
will  produce  but  a  feeble  effect  on  the  reader  s  mind, 
can  only  repeat  my  assurance,  that  I  do  not  speak  without 
good  evidence. 


CHANGES  OF  HABIT  OR  INSTINCT. 


247 

INHERITED  CHANGES  OF  HABIT  OR  IHSTIHCT  IH  DOMES¬ 
TICATED  AHIMALS. 

.  The  possibility,  or  even  probability,  of  inherited  varia¬ 
tions  of  instinct  in  a  state  of  nature  will  be  strengthened 
by  briefly  considering  a  few  cases  under  domestication. 
We  shall  thus  be  enabled  to  see  the  part  which  habit  and 
the  selection  of  so-called  spontaneous  variations  have  played 
in  modifying  the  mental  qualities  of  our  domestic  animals. 
It  is  notorious  how  much  domestic  animals  vary  in  their 
mental  qualities.  With  cats,  for  instance,  one  naturally 
takes  to  catching  rats,  and  another  mice,  and  these  ten¬ 
dencies  are  known  to  be  inherited.  One  cat,  according  to 
Mr.  St.  John,  always  brought  home  game  birds,  another 
hares  or  rabbits,  and  another  hunted  on  marshy  ground  and 
almost  nightly  caught  woodcocks  or  snipes.  A  number  of 
curious  and  authentic  instances  could  be  given  of  various 
shades  of  disposition  and  of  taste,  and  likewise  of  the  oddest 
tricks,  associated  with  certain  frames  of  minds  or  periods 
of  time,  being  inherited.  But  let  us  look  to  the  familiar 
case  of  the  breeds  of  the  dogs:  it  cannot  be  doubted  that 
young  pointers  (I  have  myself  seen  striking  instances)  will 
sometimes  point  and  even  back  other  dogs  the  very  first 
time  that  they  are  taken  out;  retrieving  is  certainly  in 
some  degree  inherited  by  retrievers;  and  a  tendency  to  run 
round,  instead  of  at,  a  flock  of  sheep,  by  shepherd  dogs. 

I  cannot  see  that  these  actions,  performed  without  experi¬ 
ence  by  the  young,  and  in  nearly  the  same  manner  by  each 
individual,  performed  with  eager  delight  by  each  breed, 
and  without  the  end  being  known — for  the  young  pointer 
can  no  more  know  that  he  points  to  aid  his  master,  than 
the  white  butterfly  knows  why  she  lavs  her  eggs  on  the  leal 
of  the  cabbage— I  cannot  see  that  these  actions  differ 
essentially  from  true  instincts.  If  we  were  to  behold  one 
kind  of  wolf,  when  young  and  without  any  training,  as 
soon  as  it  scented  its  prey,  stand  motionless  like  a  statue, 
and  then  slowly  crawl  forward  with  a  peculiar  gait;  and 
another  kind  of  wolf  rushing  round,  instead  of  at,  a  herd 
of  deer,  and  driving  them.  to  .  a  distant  point,  we  should 
assuredly  call  these  actions  instinctive.  Domestic  instincts, 
as  they,  may  be  called,  are  certainly  far  less  fixed  than 
natural  instincts;  but  they  have  been  acted  on  by  far  less 


248 


CHANGES  OF  HABIT  OR  INSTINCT 

rigorous  selections,  and  have  been  transmitted  for  ail 
incomparably  shorter  period,  under  less  fixed  conditions  of 

life. 

How  strongly  these  domestic  instincts,  habits,  and 
dispositions  are  inherited,  and  how  curiously  thev 
become  mingled,  is  well  shown  when  different  breeds  of 
dogs  are  crossed.  Thus  it  is  known  that  a  cross  with  a 
bull-dog  has  affected  for  many  generations  the  courage  and 
obstinacy  of  greyhounds;  and  a  cross  with  a  greyhound 
has  given  to  a  whole  family  of  shepherd-dogs  a  tendency 
to  hunt  hares.  These  domestic  instincts,  when  thus  tested 
by  crossing,  resemble  natural  instincts,  which  in  a  like 
manner  become  curiously  blended  together,  and  foi  a  long 
period  exhibit  traces  of  the  instincts  of  either  parent:  for 
example,  Le  Roy  describes  a  dog,  whose  great-giandfather 
was  a  wolf,  and  this  dog  showed  a  trace  of  its  wild  parent¬ 
age  only  in  one  way,  by  not  coming  in  a  straight  line  to 
his  master,  when  called. 

Domestic  instincts  are  sometimes  spoken  of  as  actions 
which  have  become  inherited  solely  from  long-continued 
and  compulsory  habit;  but  this  is  not  true.  No  one  would 
ever  have  thought  of  teaching,  or  probably  could  have 
taught,  the  tumbler-pigeon  to  tumble— an  action  which, 
as  I  have  witnessed,  is  performed  by  young  birds,  that  have 
never  seen  a  pigeon  tumble.  We  may  believe  that  some 
one  pigeon  showed  a  slight  tendency  to  this  strange  habit, 
and  that  the  long-continued  selection  of  the  best  individ¬ 
uals  in  successive  generations  made  tumblers  what  they 
now  are;  and  near  Glasgow  there  are  house-tumblers,  as  I 
hear  from  Mr.  Brent,  which  can  not  fly  eighteen  inches 
high  without  going  head  over  heels.  It  may.  be  doubted 
whether  any  one  would  have  thought  of  training  a  dog  to 
point,  had  not  some  one  dog  naturally  shown  a  tendency 
in  this  line;  and  this  is  known  occasionally  to.  happen,  a3 
I  once  saw,  in  a  pure  terrier:  the  act  of  pointing  is  prob¬ 
ably,  as  many  have  thought,  only  the  exaggerated  pause  of 
an  animal  preparing  to  spring  on  its  prey.  When  the  first 
tendency  to  point  was  once  displayed,  methodical  selection 
and  the  inherited  effects  of  compulsory  training  in  each 
successive  generation  would  soon  complete  the  work;  and 
unconscious  selection  is  still  in  progress,  as  each  man  tries 
to  procure,  without  intending  to  improve  the  breed,  dogs 


IN  DOMESTIC  A  TED  ANIMALS. 


249 


which  stand  and  hunt  best.  On  the  other  hand,  habit 
alone  in  some  cases  has  sufficed;  hardly  any  animal  is 
more  difficult  to  tame  than  the  young  of  the  wild  rabbit; 
scarcely  any  animal  is  tamer  than  the  young  of  the  tame 
rabbit;  but  I  can  hardly  suppose  that  domestic  rabbits  have 
often  been  selected  for  tameness  alone;  so  that  we  must 
attribute  at  least  the  greater  part  of  the  inherited  change 
from  extreme  wildness  to  extreme  tameness,  to  habit  and 
long-continued  close  confinement. 

Natural  instincts  are  lost  under  domestication:  a  re¬ 
markable  instance  of  this  is  seen  in  those  breeds  of  fowls 
which  very  rarely  or  never  become  “broody,”  that  is,  never 
wish  to  sit  on  their  eggs.  Familiarity  alone  prevents  our 
seeing  how  largely  and  how  permanently  the  minds  of  our 
domestic  animals  have  been  modified.  It  is  scarcely  pos¬ 
sible  to  doubt  that  the  love  of  man  has  become  instinctive 
in  the  dog.  All  wolves,  foxes,  jackals  and  species  of  the  cat 
genus,  when  kept  tame,  are  most  eager  to  attack  poultry, 
sheep  and  pigs;  and  this  tendency  has  been  found  incur¬ 
able  in  dogs  which  have  been  brought  home  as  puppies  from 
countries  such  as  Tierra  del  Fuego  and  Australia,  where  the 
savages  do  not  keep  these  domestic  animals.  How  rarely,  on 
the  other  hand,  do  our  civilized  dogs,  even  when  quite 
young,  require  to  be  taught  not  to  attack  poultry,  sheep  and 
pigs!  No  doubt  they  occasionally  do  make  an  attack,  and 
are  then  beaten;  and  if  not  cured,  they  are  destroyed; 
so  that  habit  and  some  degree  of  selection  have  proba¬ 
bly  concurred  in  civilizing  by  inheritance  our  dogs.  On 
the  other  hand,  young  chickens  have  lost  wholly  by  habit, 
that  fear  of  the  dog  and  cat  which  no  doubt  was  originally 
instinctive  in  them,  for  I  am  informed  by  Captain  Hutton 
that  the  young  chickens  of  the  parent  stock,  the  Gallus 
bankiva,  when  reared  in  India  under  a  hen,  are  at  first  ex¬ 
cessively  wild.  So  it  is  with  young  pheasants  reared  in 
England  under  a  hen.  It  is  not  that  chickens  have  lost  all 
fear,  but  fear  only  of  dogs  and  cats,  for  if  the  hen  gives 
the  danger  chuckle  they  will  run  (more  especially  young 
turkeys)  from  under  her  and  conceal  themselves  in  the 
surrounding  grass  or  thickets;  and  this  is  evidently  done 
for  the  instinctive  purpose  of  allowing,  as  we  see  in  wild 
ground-birds,  their  mother  to  fly  away.  But  this  instinct 
retained  by  our  chickens  has  become  useless  under  domes- 


250 


SPECIAL  INSTINCTS . 


tication,  for  the  mother  hen  has  almost  lost  by  disuse  the 
power  of  flight. 

Hence,  we  may  conclude  that  under  domestication  in¬ 
stincts  have  been  acquired  and  natural  instincts  have  been 
lost,  partly  by  habit  and  partly  by  man  selecting  and 
accumulating,  during  successive  generations,  peculiar 
mental  habits  and  actions,  which  at  first  appeared  from 
what  we  must  in  our  ignorance  call  an  accident.  In  some 
cases  compulsory  habit  alone  has  sufficed  to  produce  in¬ 
herited  mental  changes.  In  other  cases  compulsory  habit 
has  done  nothing,  and  all  has  been  the  result  of 
selection,  pursued  both  methodically  and  unconsciously; 
but  in  most  cases  habit  and  selection  have  probably 
concurred. 


SPECIAL  INSTINCTS. 

We  shall,  perhaps,  best  understand  how  instincts  in  a 
state  of  nature  have  become  modified^  by  selection  by  con¬ 
sidering  a  few  cases.  I  will  select  only  three,  namely,  the 
instinct  which  leads  the  cuckoo  to  lay  her  eggs  in  other 
birds'  nests;  the  slave-making  instinct  of  certain  ants,  and 
the  cell-making  power  of  the  hive-bee.  These  two  latter 
instincts  have  generally  and  justly  been  ranked  by  natural¬ 
ists  as  the  most  wonderful  of  all  known  instincts. 

INSTINCTS  OF  THE  CUCKOO. 

It  is  supposed  by  some  naturalists  that  the  more  imme¬ 
diate  cause  of  the  instinct  of  the  cuckoo  is  that  she  lays 
her  eggs,  not  daily,  but  at  intervals  of  two  or  three  days, 
so  that  if  she  were  to  make  her  own  nest  and  sit  on  her 
own  eggs,  those  first  laid  would  have  to  be  left  for  some 
time  unincubated  or  there  would  be  eggs  and  young  birds 
of  different  ages  in  the  same  nest.  If  this  were  the  case 
the  process  of  laying  and  hatching  might  be  inconveni¬ 
ently  long,  more  especially  as  she  migrates  at  a  very 
early  period,  and  the  first  hatched  young  would  probably 
have  to  be  fed  by  the  male  alone.  But  the  American 
cuckoo  is  in  this  predicament,  for  she  makes  her  own  nest 
and  has  eggs  and  young  successively  hatched,  all  at  the 
same  time.  It  has  been  both  asserted  and  denied  that 


INSTINCTS  OF  TIIE  CUCKOO. 


251 


the  American  cuckoo  occasionally  lays  her  eggs  in  other 
birds'  nests;  but  I  have  lately  heard  from  Dr.  Merrill, 
of  Iowa,  that  he  once  found  in  Illinois  a  young  cuckoo, 
together  with  a  young  jay  in  the  nest  of  a  blue  jay  (Gar- 
rulus  cristatus);  and  as  both  were  nearly  full  feathered, 
there  could  be  no  mistake  in  their  identification.  I  could 
also  give  several  instances  of  various  birds  which  have 
been  known  occasionally  to  lay  their  eggs  in  other  birds' 
nests.  Now  let  us  suppose  that  the  ancient  progenitor  of 
our  European  cuckoo  had  the  habits  of  the  American 
cuckoo,  and  that  she  occasionally  laid  an  egg  in  another 
bird's  nest.  If  the  old  bird  profited  by  this  occasional 
habit  through  being  enabled  to  emigrate  earlier  or  through 
any  other  cause;  or  if  the  young  were  made  more  vigorous 
by  advantage  being  taken  of  the  mistaken  instinct  of 
another  species  than  when  reared  by  their  own  mother, 
encumbered  as  she  could  hardly  fail  to  be  by  having  eggs 
and  young  of  different  ages  at  the  same  time,  then  the  old 
birds  or  the  fostered  young  would  gain  an  advantage.  And 
analogy  would  lead  us  to  believe  that  the  young  thus  reared 
would  be  apt  to  follow  by  inheritance  the  occasional  and 
aberrant  habit  of  their  mother,  and  in  their  turn  would  be 
apt  to  lay  their  eggs  in  other  birds'  nest,  and  thus  be  more 
successful  in  rearing  their  young.  By  a  continued  process 
of  this  nature,  I  believe  that  the  strange  instinct  of  our 
cuckoo  has  been  generated.  It  has,  also,  recently  been 
ascertained  on  sufficient  evidence,  by  Adolf  Muller,  that 
the  cuckoo  occasionally  lays  her  eggs  on  the  bare  ground, 
sits  on  them  and  feeds  her  voung.  This  rare  event  is  prob¬ 
ably  a  case  of  reversion  to  the  long-lost,  aboriginal  instinct 
of  nidification. 

It  has  been  objected  that  I  have  not  noticed  other  re¬ 
lated  instincts  and  adaptations  of  structure  in  the  cuckoo, 
which  are  spoken  of  as  necessarily  co-ordinated.  But  in 
all  cases,  speculation  on  an  instinct  known  to  us  only  in  a 
single  species,  is  useless,  for  we  have  hitherto  had  no 
facts  to  guide  us.  Until  recently  the  instincts  of  the 
European  and  of  the  non-parasitic  American  cuckoo  alone 
were  known;  now,  owing  to  Mr.  Ramsay’s  observations,  we 
have  learned  something  about  three  Australian  species, 
which  lay  their  eggs  in  other  birds'  nests.  The  chief 
points  to  be  referred  to  are  three:  first,  that  the  eommor 


SPECIAL  INSTINCTS. 


252 

cuckoo,  with  rare  exceptions,  lays  only  one  egg  in  a  nest, 
so  that  the  large  and  voracious  young  bird  receives  ample 
food.  Secondly,  that  the  eggs  are  remarkably  small,  not 
exceeding  those  of  the  skylark — a  bird  about  one-foui  th  as 
large  as  the  cuckoo.  That  the  small  size  of  the  egg  is  a 
real  case  of  adaptation  we  may  infer  from  the  fact  of  the 
non-parasitic  American  cuckoo  laying  full-sized  eggs. 
Thirdly,  that  the  young  cuckoo,  soon  after  birth,  has  the 
.'instinct,  the  strength  and  a  properly  shaped  back  for  eject¬ 
ing  its  foster-brothers,  which  then  perish  from  cold  and 
huno-er.  This  has  been  boldly  called  a  beneficent  arrange¬ 
ment,  in  order  that  the  young  cuckoo  may  get  sufficient 
food,  and  that  its  foster-brothers  may  perish  before  they 

*iad  acquired  much  feeling!  # 

Turning  now  to  the  Australian  species,  though  these 
birds  generally  lay  only  one  egg  in  a  nest,  it  is  not  rare  to  find 
two  and  even  three  eggs  in  the  same  nest.  In  the  bronze 
cuckoo  the  eggs  vary  greatly  in  size,  from  eight  to  ,en 
lines  in  length.  Now,  if  it  had  been  of  an  advantage  to 
this  species  to  have  laid  eggs  even  smaller  than  those  now 
laid,  so  as  to  have  deceived  certain  foster-parents,  or,  as  is 
more  probable,  to  have  been  hatched  within  a  shorter 
period  (for  it  is  asserted  that  there  is  a  relation  between 
the  size  of  eggs  and  the  period  of  their  incubation),  then 
there  is  no  difficulty  in  believing  that  a  race  or  species 
might  have  been  formed  which  would  have  laid  smaller  and 
smaller  eggs;  for  these  would  have  been  more  safely  hatched 
and  reared?  Mr.  Ramsay  remarks  that  two  of  the  Australian 
cuckoos,  when  they  lay  their  eggs  in  an  open  nest,  mani¬ 
fest  a  decided  preference  for  nests  containing  eggs  similar 
in  color  to  their  own.  The  European  species  apparently 
manifests  some  tendency  toward  a  similar  instinct,  but  not 
rarely  departs  from  it,  as  is  shown  by  her  laying  her  dull 
and  pale-colored  eggs  in  the  nest  of  the  hedge-warblei 
with  bright  greenish-blue  eggs.  Had  our  cuckoo  invari¬ 
ably  displayed  the  above  instinct,  it  would  assuredly  have 
been  added  to  those  which  it  is  assumed  must  all  have 
been  acquired  together.  The  eggs  of  the  Australian  bronze 
cuckoo  vary,  according  to  Mr.  Ramsay,  to  an  extraordinary 
degree  in  color;  so  that  in  this  respect,  as  well  as  in  size, 
natural  selection  might  have  secured  and  fixed  any  advan¬ 
tageous  variation. 


INSTINCTS  OF  THE  MOLOTHRUS. 


253 


In  the  case  of  the  European  cuckoo,  the  offspring  of  the 
foster-parents  are  commonly  ejected  from  the  nest  within 
three  days  after  the  cuckoo  is  hatched;  and  as  the  latter 
at  this  age  is  in  a  most  helpless  condition,  Mr.  Gfould  was 
formerly  inclined  to  believe  that  the  act  of  ejection  was 
performed  by  the  foster-parents  themselves.  But  he  has 
now  received  a  trustworthy  account  of  a  young  cuckoo 
which  was  actually  seen,  while  still  blind  and"  not  able  even 
to  hold  up  its  own  head,  in  the  act  of  ejecting  its  foster- 
brothers.  One  of  these  was  replaced  in  the  nest  by  the 
observer,  and  was  again  thrown  out.  With  respect  to  the 
means  by  which  this  strange  and  odious  instinct  was  ac¬ 
quired,  if  it  were  of  great  importance  for  the  young  cuckoo, 
as  is  probably  the  case,  to  receive  as  much  food  as  possible 
soon  after  birth,  I  can  see  no  special  difficulty  in  its  having 
gradually  acquired,  during  successive  generations,  the  blind 
desire,  the  strength,  and  structure  necessary  for  the  work 
of  ejection;  for  those  cuckoos  which  had  such  habits  and 
structure  best  developed  would  be  the  most  securely  reared. 
The  first  step  toward  the  acquisition  of  the  proper  instinct 
might  have  been  mere  unintentional  restlessness  on  the 
part  of  the  young  bird,  when  somewhat  advanced  in  age 
and  strength;  the  habit  having  been  afterward  improved, 
and  transmitted  to  an  earlier  age.  I  can  see  no  more  diffi¬ 
culty  in  this  than  in  the  unhatched  young  of  other  birds 
acquiring  the  instinct  to  break  through  their  own  shells; 
or  than  in  young  snakes  acquiring  in  their  upper  jaws,  as 
Owen  has  remarked,  a  transitory  sharp  tooth  for  cutting 
through  the  tough  egg-shell.  For  if  each  part  is  liable  to 
individual  variations  at  all  ages,  and  the  variations  tend  to 
be  inherited  at  a  corresponding  or  earlier  age — proposi¬ 
tions  which  cannot  be  disputed— then  the  instincts  and 
structure  of  the  young  could  be  slowly  modified  as  surely 
as  those  of  the  adult;  and  both  cases  must  stand  or  fall 
together  with  the  whole  theory  of  natural  selection. 

borne  species  of  Molothrus,  a  widely  distinct  genus  of 
American  birds,  allied  to  our  starlings,  have  parasitic 
habits  like  those  of  the  cuckoo;  and  the  species  present  an 
interesting  gradation  in  the  perfection  of  their  instincts. 
The  sexes  of  Molothrus  badius  are  stated  by  an  excellent 
observer,  Mr.  Hudson,  sometimes  to  live  promiscuously 
together  in  flocks,  and  sometimes  to  pair.  They  either 


254 


SPECIAL  INSTINCTS . 


build  a  nest  of  their  own  or  seize  on  one  belonging  to  some 
other  bird,  occasionally  throwing  out  the  nestlings  of  the 
stranger.  They  either  lay  their  eggs  in  the  nest  thus  appro¬ 
priated,  or  oddly  enough  build  one  for  themselves  on  the  top 
of  it.  They  usually  sit  on  their  own  eggs  and  rear  their  own 
young;  but  Mr.  Hudson  says  it  is  probable  that  they  are  occa¬ 
sionally  parasitic,  for  he  has  seen  the  young  of  this  species 
following  old  birds  of  a  distinct  kind  and  clamoring  to  be 
fed  by  them.  The  parasitic  habits  of  another  species  of 
Molothrus,  the  M.  bonariensis,  are  much  more  highly  de¬ 
veloped  than  those  of  the  last,  but  are  still  far  from  per¬ 
fect.  This  bird,  as  far  as  it  is  known,  invariably  lays  its 
eggs  in  the  nests  of  strangers;  but  it  is  remarkable  that 
several  together  sometimes  commence  to  build  an  irregular 
untidy  nest  of  their  own,  placed  in  singular  ill-adapted 
situations,  as  on  the  leaves  of  a  large  thistle.  They  never, 
however,  as  far  as  Mr,  Hudson  has  ascertained,  complete  a 
nest  for  themselves.  They  often  lay  so  many  eggs— from 
fifteen  to  twenty — in  the  same  foster-nest,  that  few  or  none 
can  possibly  be  hatched.  They  have,  moreover,  the  extra¬ 
ordinary  habit  of  pecking  holes  in  the  eggs,  whether  of 
their  own  species  or  of  their  foster  parents,  which  they  find 
in  the  appropriated  nests.  They  drop  also  many  eggs  on 
the  bare  ground,  which  are  thus  wasted.  A  third  species, 
the  M.  pecoris  of  North  America,  has  acquired  instinct?- 
as  perfect  as  those  of  the  cuckoo,  for  it  never  lays  more 
than  one  egg  in  a  foster-nest,  so  that  the  }7oung  bird  is 
securely  reared.  Mr.  Hudson  is  a  strong  disbeliever  in 
evolution,  but  he  appears  to  have  been  so  much  struck  by 
the  imperfect  instincts  of  the  Molothrus  bonariensis  that 
he  quotes  my  words,  and  asks,  “  Must  we  consider  these 
habits,  not  as  especially  endowed  or  created  instincts,  but 
as  small  consequences  of  one  general  law,  namely, 
transition  ?” 

Various  birds,  as  has  already  been  remarked,  occasionally 
iay  their  eggs  in  the  nests  of  other  birds.  This  habit  is 
not  very  uncommon  with  the  Gallinaceas,  and  throws  some 
light  on  the  singular  instinct  of  the  ostrich.  In  this 
family  several  hen  birds  unite  and  lay  first  a  few  eggs  in 
one  nest  and  then  in  another;  and  these  are  hatched  by 
tbe  males.  This  instinct  may  probably  be  accounted  for  by 
the  fact  of  the  hens  laying  a  large  number  of  eggs,  but,  as 


SLA  VK- MAKING  INSTINCT . 


255 


with  the  cuckoo,  at  intervals  of  two  or  three  days.  The 
instinct,  however,  of  the  American  ostrich,  as  in  the  case 
of  the  Molotlirus  bonariensis,  has  not  as  yet  been  per¬ 
fected;  for  a  surprising  number  of  eggs  lie  strewed  over 
the  plains,  so  that  in  one  day’s  hunting  I  picked  up  no  less 
than  twenty  lost  and  wasted  eggs. 

Many  bees  are  parasitic,  and  regularly  lay  their  eggs  in 
the  nests  of  other  kinds  of  bees.  This  case  is  more  re¬ 
markable  than  that  of  the  cuckoo;  for  these  bees  have  not 
only  had  their  instincts  but  their  structure  modified  in 
accordance  with  their  parasitic  habits;  for  they  do  not 
possessess  the  pollen-collecting  apparatus  which  would  have 
been  indispensable  if  they  had  stored  up  food  for  their  own 
young.  Some  species  of  Sphegidae  (wasp-like  insects)  are 
likewise  parasitic;  and  M.  Fabre  has  lately  shown  good 
reason  for  believing  that,  although  the  Tachytes  nigra  gen¬ 
erally  makes  it  own  burrow  and  stores  it  with  paralyzed 
prey  for  its  own  larvae,  yet  that,  when  this  insect  finds  a 
burrow  already  made  and  stored  by  another  sphex,  it  takes 
advantage  of  the  prize,  and  becomes  for  the  occasion  par¬ 
asitic.  In  this  case,  as  with  that  of  the  Molotlirus  or 
cuckoo,  I  can  see  no  difficulty  in  natural  selection  making 
an  occasional  habit  permanent,  if  of  advantage  to  the 
species,  and  if  the  insect  whose  nest  and  stored  food  are 
feloniously  appropriated,  be  not  thus  exterminated. 

SLAVE-MAKING  INSTINCT. 

This  remarkable  instinct  was  first  discovered  in  the  For¬ 
mica  (Polyerges)  rufescens  by  Pierre  Huber,  a  better 
observer  even  than  his  celebrated  father.  This  ant  is  ab¬ 
solutely  dependent  on  its  slaves;  without  their  aid,  the 
species  would  certainly  become  extinct  in  a  single  year. 
The  males  and  fertile  females  do  no  work  of  any  kind,  and 
the  workers  or  sterile  females,  though  most  energetic  and 
courageous  in  capturing  slaves,  do  no  other  work.  They 
are  incapable  of  making  their  own  nests,  or  of  feeding 
their  own  larvae.  When  the  old  nest  is  found  incon¬ 
venient,  and  they  have  to  migrate,  it  is  the  slaves  which 
determine  the  migration,  and  actually  carry  their  masters 
in  their  jaws.  So  utterly  helpless  are  the  masters,  that 
when  Huber  shut  up  thirty  of  them  without  a  slave,  but 


256 


SPECIAL  INSTINCTS. 


with  plenty  of  food  which  they  like  best,  and  with  their 
own  larvas  and  pupae  to  stimulate  them  to  work,  they  did 
nothing;  they  could  not  even  feed  themselves,  and  many 
perished  of  hunger.  Huber  then  introduced  a  single  slave 
(F.  fusca),  and  she  instantly  set  to  work,  fed  and  saved 
the  survivors;  made  some  cells  and  tended  the  larvae,  and 
put  all  to  rights.  What  can  be  more  extraordinary  than 
these  well-ascertained  facts  ?  If  we  had  not  known  of  any 
other  slave-making  ant,  it  would  have  been  hopeless  to 
speculate  how  so  wonderful  an  instinct  could  have  been, 
perfected. 

Another  species,  Formica  sanguinea,  was  likewise  first 
discovered  by  P.  Huber  to  be  a  slave-making  ant.  This 
species  is  found  in  the  southern  parts  of  England,  and  its 
habits  have  been  attended  to  by  Mr.  F.  Smith,  of  the  Brit¬ 
ish  Museum,  to  whom  I  am  much  indebted  for  information 
on  this  and  other  subjects.  Although  fully  trusting  to  the 
statements  of  Huber  and  Mr.  Smith,  I  tried  to  approach 
the  subject  in  a  skeptical  frame  of  mind,  as  any  one  may 
well  be  excused  for  doubting  the  existence  of  so  extraordi¬ 
nary  an  instinct  as  that  of  making  slaves.  Hence,  I  will 
give  the  observations  which  I  made  in  some  little  detail. 
I  opened  fourteen  nests  of  F.  sanguinea,  and  found  a  few 
slaves  in  all.  Males  and  fertile  females  of  the  slave  species 
(F.  fusca)  are  found  only  in  their  own  proper  communi¬ 
ties,  and  have  never  been  observed  in  the  nests  of  F.  san¬ 
guinea.  The  slaves  are  black  and  not  above  half  the  size 
of  their  red  masters,  so  that  the  contrast  in  their  appear¬ 
ance  is  great.  When  the  nest  is  slightly  disturbed,  the 
slaves  occasionally  come  out,  and  like  their  masters  are  much 
agitated  and  defend  the  nest:  when  the  nest  is  much  dis¬ 
turbed,  and  the  larvaB  and  pupae  are  exposed,  the  slaves 
work  energetically  together  with  their  masters  in  carrying 
them  away  to  a  place  of  safety.  Hence,  it  is  clear  that 
the  slaves  feel  quite  at  home.  During  the  months  of  June 
and  J uly,  on  three  successive  years,  I  watched  for  many 
hours  several  nests  in  Surrey  and  Sussex,  and  never  saw  a 
slave  either  leave  or  enter  a  nest.  As,  during  these 
months,  the  slaves  are  very  few  in  number,  I  thought  that 
they  might  behave  differently  when  more  numerous;  but 
Mr.  Smith  informs  me  that  he  has  watched  the  nests  at 
various  hours  during  May,  June  and  August,  both  in  Sur- 


SLA  VE-MAKING  INSTINCT. 


257 


rey  and  Hampshire,  and  has  never  seen  the  slaves,  though 
present  in  large  numbers  in  August,  either  leave  or  enter 
the  nest.  Hence,  he  considers  them  as  strictly  household 
slaves.  The  masters,  on  the  other  hand,  may  be  con¬ 
stantly  seen  bringing  in  materials  for  the  nest,  and  food  of 
all  kinds.  During  the  year  1860,  however,  in  the  month 
of  J uly,  I  came  across  a  community  with  an  unusually 
large  stock  of  slaves,  and  I  observed  a  few  slaves  mingled 
with  their  masters  leaving  the  nest,  and  marching  along 
the  same  road  to  a  tall  Scotch  fir-tree,  twentv-five  yards 
distant,  which  they  ascended  together,  probably  in  search 
of  aphides  or  cocci.  According  to  Huber,  who  had  ample 
opportunities  for  observation,  the  slaves  in  Switzerland 
habitually  work  with  their  masters  in  making  the  nest, 
and  they  alone  open  and  close  the  doors  in  the  morning  and 
evening;  and,  as  Huber  expressly  states,  their  principle 
office  is  to  search  for  aphides.  This  difference  in  the  usual 
habits  of  the  masters  and  slaves  in  the  two  countries,  prob¬ 
ably  depends  merely  on  the  slaves  being  captured  in  greater 
numbers  in  Switzerland  than  in  England. 

One  day  I  fortunately  witnessed  a  migration  of  F.  san- 
guina  from  one  nest  to  another,  and  it  was  a  most  interest¬ 
ing  spectacle  to  behold  the  masters  carefully  carrying  their 
slaves  in  their  jaws  instead  of  being  carried  by  them,  as  in 
the  case  of  F.  rufescens.  Another  day  my  attention  was 
struck  by  about  a  score  of  the  slave-makers  haunting  the 
same  spot,  and  evidently  not  in  search  of  food;  they 
approached  and  were  vigorously  repulsed  by  an  independ¬ 
ent  community  of  the  slave-species  (F.  fusca);  sometimes 
as  many  as  three  of  these  ants  clinging  to  the  legs  of  the 
slave-making  F.  sanguinea.  The  latter  ruthlessly  killed 
their  small  opponents  and  carried  their  dead  bodies  as 
food  to  their  nest,  twenty-nine  yards  distant;  but  they  were 
prevented  from  getting  any  pupae  to  rear  as  slaves.  I  then 
dug  up  a  small  parcel  of  the  pupae  of  F.  fusca  from  another 
nest,  and  put  them  down  on  a  bare  spot  near  the  place  of 
combat;  they  were  eagerly  seized  and  carried  off  by  the 
tyrants,  who  perhaps  fancied  that,  after  all,  they  had  been 
victorious  in  their  late  combat. 

At  the  same  time  I  laid  on  the  same  place  a  small  parcel 
of  the  pupae  of  another  species,  F.  flava,  with  a  few  of 
these  little  yellow  ants  still  clinging  to  the  fragments  of 


SPECIAL  INSTINCTS . 


258 

their  nest.  This  species  is  sometimes,  though  rarely, 
made  into  slaves,  as  has  been  described  by  Mr.  Smith. 
Although  so  small  a  species,  it  is  very  courageous,  and  I 
have  seen  it  ferociously  attack  other  ants.  In  one  instance 
I  found  to  my  surprise  an  independent  community  of  F. 
flava  under  a  stone  beneath  a  nest  of  the  slave-making  h. 
sanguinea;  and  when  I  had  accidentally  disturbed  both 
nests,  the  little  ants  attacked  their  big  neighbors  with  sun 
prising  courage.  Now  I  was  curious  to  ascertain  whether 
F.  sanguinea  could  distinguish  the  pupae  of  F.  fusca, 
which  they  habitually  make  into  slaves,  from  those  of  the 
little  and  furious  F.  flava,  which  they  rarely  capture,  and  it 
was  evident  that  they  did  at  once  distinguish  them;  for  we 
have  seen  that  they  eagerly  and  instantly  seized  the  pupae 
of  F.  fusca,  whereas  they  were  much  terrified  when  they 
came  across  the  pupae,  or  even  the  earth  from  the  nest,  of 
F.  flava,  and  quickly  ran  away;  but  in  about  a  quarter  of 
an  hour,  shortly  after  all  the  little  yellow  ants  had  crawled 
awav,  they  took  heart  and  carried  off  the  pupae. 

One  evening  I  visited  another  community  of  F.  san¬ 
guinea,  and  found  a  number  of  these  ants  returning  home 
and  entering  their  nests,  carrying  the  dead  bodies  of  F. 
fusca  (showing  that  it  was  not  a  migration)  and  numerous 
pupae.  I  traced  a  long  file  of  ants  burdened  with  booty, 
for  about  forty  yards  back,  to  a  very  thick  clump  of  heath, 
whence  I  saw  the  last  individual  of  h.  sanguinea  emeige, 
carrying  a  pupa;  but  I  was  not  able  to  find  the  desolated 
nest  in  the  thick  heath.  The  nest,  however,  must  have 
been  close  at  hand,  for  two  or  three  individuals  of  F.  fusca 
were  rushing  about  in  the  greatest  agitation,  and  one  >vas 
perched  motionless  with  its  own  pupa  in  its  mouth  on  the 
top  of  a  spray  of  heath,  an  image  of  despair  over  its  ravaged 

home. 

Such  are  the  facts,  though  they  did  not  need  confirma¬ 
tion  by  me,  in  regard  to  the  wonderful  instinct  of  making 
slaves.  Let  it  be  observed  what  a  contrast  the  instinctive 
habits  of  F.  sanguinea  present  with  those  of.  the  conti¬ 
nental  F.  rufescens.  The  latter  does  not  build  its  own 
nest,  does  not  determine  its  own  migrations,  does  not  col¬ 
lect  food  for  itself  or  its  young,  and  cannot  even  feed 
itself:  it  is  absolutely  dependent  on  its  numerous  slaves. 
Formica  sanguinea,  on  the  other  hand,  possesses  much 


CELL-MAKING  INSTINCT. 


259 


fewer  slaves,  and  in  the  early  part  of  the  summer  extremely 
few:  the  masters  determine  when  and  where  a  new  nest 
shall  be  formed,  and  when  they  migrate,  the  masters  carry 
the  slaves.  Both  in  Switzerland  and  England  the  slaves 
seem  to  have  the  exclusive  care  of  the  larvse,  and  the  mas¬ 
ters  alone  go  on  slave-making  expeditions.  In  Switzerland 
the  slaves  and  masters  work  together,  making  and  bringing 
materials  for  the  nest;  both,  but  chiefly  the  slaves,  tend 
and  milk,  as  it  may  be  called,  their  aphides;  and  thus  both 
collect  food  for  the  community.  In  England  the  masters 
alone  usually  leave  the  nest  to  collect  building  materials 
and  food  for  themselves,  their  slaves  and  larv®.  So  that 
the  masters  in  this  country  receive  much  less  service  from 
their  slaves  than  they  do  in  Switzerland. 

By  what  steps  the  instinct  of  F.  sanguinea  originated  I 
will  not  pretend  to  conjecture.  But  as  ants  which  are  not 
slave-makers  will,  as  I  have  seen,  carry  off  the  pupae  of 
other  species,  if  scattered  near  their  nests,  it  is  possible 
that  such  pup®  originally  stored  as  food  might  become 
developed;  and  the  foreign  ants  thus  unintentionally  reared 
would  then  follow  their  proper  instincts,  and  do  what  work 
they  could.  If  their  presence  proved  useful  to  the  species 
which  had  seized  them — if  it  were  more  advantageous  to 
this  species,  to  capture  workers  than  to  procreate  them — 
the  habit  of  collecting  pup®,  originally  for  food,  might  by 
natural  selection  be  strengthened  and  rendered  permanent 
for  the  very  different  purpose  of  raising  slaves.  When  the 
instinct  was  once  acquired,  if  carried  out  to  a  much  less 
extent  even  than  in  our  British  F.  sanguinea,  which,  as  we 
have  seen,  is  less  aided  by  its  slaves  than  the  same  species 
in  Switzerland,  natural  selection  might  increase  and  modify 
the  instinct — always  supposing  each  modification  to  be  of 
use  to  the  species — until  an  ant  w^as  formed  as  abjectly 
dependent  on  its  slaves  as  is  the  Formica  rufescens. 

CELL-MAKING  INSTINCT  OF  TIIE  HIYE-BEE. 

I  will  not  here  enter  on  minute  details  on  this  subject, 
but  will  merely  give  an  outline  of  the  conclusions  at  which 
I  have  arrived.  He  must  be  a  dull  man  who  can  examine 
the  exquisite  structure  of  a  comb,  so  beautifully  adapted 
to  its  end,  without  enthusiastic  admiration.  We  hear  from 


260 


SPECIAL  INSTINCTS. 


mathematicians  that  bees  have  practically  solved  a  recon¬ 
dite  problem,  and  have  made  their  cells  of  the  proper 
shape  to  hold  the  greatest  possible  amount  of  honey,  with 
the  least  possible  consumption  of  precious  wax  in  their 
construction.  It  has  been  remarked  that  a  skillful  work¬ 
man  with  fitting  tools  and  measures,  would  find  it  very 
difficult  to  make  cells  of  wax  of  the  true  form,  though  this 
is  effected  by  a  crowd  of  bees  working  in  a  dark  hive. 
Granting  whatever  instincts  you  please,  it  seems  at  first 
quite  inconceivable  how  they  can  make  all  the  necessary 
angles  and  planes,  or  even  perceive  when  they  are  correctly 
made.  But  the  difficulty  is  not  nearly  so  great  as  at  first 
appears:  all  this  beautiful  work  can  be  shown,  I  think,  to 
follow  from  a  few  simple  instincts. 

I  was  led  to  investigate  this  subject  by  Mr.  Waterhouse, 
who  has  shown  that  the  form  of  the  cell  stands  in  close  re¬ 
lation  to  the  presence  of  adjoining  cells;  and  the  following 
view  may,  perhaps,  be  considered  only  as  a  modification  of 
his  theory.  Let  us  look  to  the  great  principle  of  gradation, 
and  see  whether  Nature  does  not  reveal  tous  her  method  of 
work.  At  one  end  of  a  short  series  we  have  humble-bees, 
which  use  their  old  cocoons  to  hold  honey,  sometimes 
adding  to  them  short  tubes  of  wax,  and  likewise  making 
separate  and  very  irregular  rounded  cells  of  wax.  .  At  the 
other  end  of  the  series  we  have  the  cells  of  the  hive-bee, 
placed  in  a  double  layer:  each  cell,  as  is  well  known,  is 
an  hexagonal  prism,  with  the  basal  edges  of  its  six  sides 
beveled  so  as  to  join  an  inverted  pyramid,  of  three  rhombs. 
These  rhombs  have  certain  angles,  and  the  three  which 
form  the  pyramidal  base  of  a  single  cell  on  one  side  of  the 
comb  enter  into  the  composition  of  the  bases  of  three  ad¬ 
joining  cells  on  the  opposite  side.  In  the  series  between 
the  extreme  perfection  "of  the  cells  of  the  hive-bee  and  the 
simplicity  of  those  of  the  humble-bee  we  have  the  cells  of 
the  Mexican  Melipona  domestica,  carefully  described  and 
figured  by  Pierre  Iluber.  The  Melipona  itself  is  interme¬ 
diate  in  structure  between  the  hive  and  humble-bee,  but 
more  nearly  related  to  the  latter;  it  forms  a  nearly  regular 
waxen  comb  of  cylindrical  cells,  in  which  the  young  are 
hatched,  and,  in  addition,  some  large  cells  of  wax  for  hold¬ 
ing  honey.  These  latter  cells  are  nearly,  spherical  and  of 
nearly  equal  sizes,  and  are  aggregated  into  an  irregular 


BURT’S  HOME  LIBRARY.  Cloth.  Oilt  Tof i.  Price,  $L(KS 


Surgeon’s  Daughter.  By  Sir  Walter 
Scott. 

Swinburne's  Poems.  By  A.  C.  Swin¬ 
burne. 

Swiss  Family  Robinson.  By  Jean 
Rudolph  Wyss. 

Taking  the  Bastile.  By  Alexandre 
Dumas. 

Tale  of  Two  Cities.  By  Chas. 
Dickens. 

Tales  from  Shakespeare.  By  Chas. 
and  Mary  Lamb. 

Tales  of  a  Traveller.  By  Washington 
Irving. 

Talisman.  By  Sir  Walter  Scott. 

Tanglewood  Tales.  By  Nathaniel 
Hawthorne. 

Tempest  and  Sunshine.  By  Mary  J 
Holmes. 

Ten  Nights  in  a  Bar  Room.  By  T.  S 
Arthur. 

Tennyson’s  Poems.  By  Alfred  Ten¬ 
nyson. 

Ten  Years  Later.  By  Alexander 
Dumas. 

Terrible  Temptation.  By  Charles 
Reads. 

Thaddeus  of  Warsaw.  By  Jane 
Porter. 

Thelma.  By  Marie  Corelli. 

Thirty  Years*  War.  By  Frederick 
Schiller. 

Thousand  Miles  Up  the  Nile.  By 
Amelia  B.  Edwards. 

Three  Guardsmen.  By  Alexandre 
Dumas. 

Three  Men  in  a  Boat.  By  Jerome  K. 
Jerome. 

Thrift.  By  Samuel  Smiles. 

Throne  of  David.  By  Rev.  J.  H 
Ingraham. 

Toilers  of  the  Sea.  By  Victor  Hugo 

Tom  Brown  at  Oxford.  By  Thomas 
Hughes. 

Tom  Brown’s  School  Days.  By 
Thos.  Hughes. 

Tom  Burke  of  “Ours.”  By  Charles 
Lever. 

Tour  of  the  World  in  Eighty  Days. 

By  Jules  Verne. 

Treasure  Island.  By  Robert  Louis 
Stevenson. 

Twenty  Thousand  Leagues  Under  the 
Sea.  By  Jules  Verne. 

Twenty  Years  After.  By  Alexandre 
Dumas. 

Twice  Told  Tales.  By  Nathaniel 
Hawthorne. 

Two  Admirals.  By  James  Fenimore 
Cooper. 

Two  Dianas.  By  Alexandre  Dumas. 

Two  Years  Before  the  Mast.  By  R  H 
Dana,  Jr. 

Uarda.  By  George  Ebbrs. 

Uncle  Max.  By  Rosa  N.  Carey. 

Uncle  Tom’s  Cabin.  By  Harriet 
Beecher  Stowe. 

Under  Two  Flag*.  By  “Ouida." 


Utopia.  By  Sir  Thomas  More. 

Vanity  Fair.  By  Wm.  M.  Thackeray. 

Vendetta.  By  Marie  Corelli. 

Vespucius,  Americus,  Life  and  Voyages. 
By  C.  Edwards  Lester 

Vicar  of  Wakefield.  By  Oliver 
Goldsmith. 

Vicomte  de  Bragelonne.  By  Alex¬ 
andre  Dumas. 

Views  A-Foot.  By  Bayard  Taylol. 

Villette.  By  Charlotte  Bronte. 

Virginians.  By  Wm.  M.  Thackeray, 

Walden.  By  Henry  D.  Thoreau 

Washington,  George,  Life  of.  By 
jAred  Sparks. 

Washington  and  His  Generals.  By  J 
T.  Headley. 

Water  Babies.  By  Charles  Kings, 

LEY. 

Water  Witch.  By  James  Feni, 
more  Cooper. 

Waverly.  By  Sir  Walter  Scott. 

Webster,  Daniel,  Life  of.  By  Samuel 
M.  Schmucker,  LL.D. 

Webster’s  Speeches.  (Selected.) 
By  Daniel  Webster 

Wee  Wifie.  By  Rosa  N.  Carey 

Westward  Ho!  By  Charles  Kings, 

LEY. 

We  Two.  By  Edna  Lyall. 

What’s  Mine’s  Mine.  By  George 
Macdonald. 

When  a  Man’s  Single.  By  J  M 
Barrie.  •* 

White  Company.  By  A.  Conan 
Doyle. 

Whites  and  the  Blues.  By  Alex¬ 
andre  Dumas. 

Whittier’s  Poems,  (early.)  By  John 
G.  Whittier. 

Wide,  Wide  World.  By  Susan  War¬ 
ner. 

Wfiliam,  the  Conqueror,  Life  of.  By 
Edward  A.  Freeman.  LL.D 

William,  the  Silent,  Life  of.  By 
Frederick  Harrison. 

Willy  Reilly.  By  William  Carle- 
ton. 

Window  in  Thrums.  By  J.  M.  Barrie 

Wing  and  Wing.  By  James  Feni¬ 
more  Cooper. 

Wolsey,  Cardinal,  Life  of.  By  Man- 
dell  Creighton. 

Woman  in  White.  By  Wilkie  Col¬ 
lins. 


waning,  is y  iiDNA  Lyall. 
Wonder  Book.  For  Boys  and 
Girls.  By  Nathaniel  Haw¬ 
thorne. 

By  Sir  Walter  Scott. 
Married.  By  Rosa  N. 


Woodstock. 

Wooed  and 

Carey. 

Wooing  O’t.  „ . 

Wordsworth’s  Poems. 

Wordsworth. 

Wormwood.  By  Marie  Corelli. 
Wreck  of  the  Grosvenor.  By  W. 
Claes  Russeli* 


By  Mrs.  Alexander. 

By  William 


CELL-MAKING  INSTINCT. 


261 

mass*  But  the  important  point  to  notice  is,  that  these 
cells  are  always  made  at  that  degree  of  nearness  to  each 
other  that  they  would  have  intersected  or  broken  into  each 
other  if  the  spheres  had  been  completed;  but  this  is  never 
permitted,  the  bees  building  perfectly  flat  walls  of  wax  be¬ 
tween  the  spheres  which  thus  tend  to  intersect.  Hence, 
each  cell  consists  of  an  outer  spherical  portion,  and  of  two" 
three,  or  more  flat  surfaces,  according  as  the  cell  adjoins 
two,  three,  or  more  other  cells.  When  one  cell  rests  on 
three  other  cells,  which,  from  the  spheres  being  nearly  of 
the  same  size,  is  very  frequently  and  necessarily  the  case, 
the  three  flat  surfaces  are  united  into  a  pyramid;  and  this 
pyramid,  as  Huber  has  remarked,  is  manifestly  a  gross  imi¬ 
tation  of  the  three-sided  pyramidal  base  of  the  cell  of  the 
hi\  e-bee.  As  in  the  cells  of  the  hive-bee,  so  here,  the  three 
plane  surfaces  in  any  one  cell  necessarily  enter  into  the 
construction  of  three  adjoining  cells.  It  is  obvious  that 
the  Melipona  saves  wax,  and  what  is  more  important, 
labor,  by  this  manner  of  building;  for  the  flat  walls  be¬ 
tween  the  adjoining  cells  are  not  double,  but  are  of  the 
same  thickness  as  the  outer  spherical  portions,  and  yet 
each  flat  portion  forms  a  part  of  two  cells. 

Reflecting  on  this  case,  it  occurred  to  me  that  if  the  Meli¬ 
pona  had  made  its  spheres  at  some  given  distance  from 
each  other,  and  had  made  them  of  equal  sizes  and  had 
arranged  them  symmetrically  in  a  double  layer,  the  resulting- 
structure  would  have  been  as  perfect  as  the  comb  of  the 
hive-bee.  Accordingly  I  wrote  to  Professor  Miller,  of  Cam¬ 
bridge,  and  this  geometer  has  kindly  read  over  the  follow¬ 
ing  statement,  drawn  up  from  his  information,  and  tells 
me  that  it  is  strictly  correct : 

If  a  number  of  equal  spheres  be  described  with  their 
centers  placed  in  two  parallel  layers;  with  the  center  of 
each  sphere  at  the  distance  of  radius  X  */  2,  or  radius 
X  1.41421  (or  at  some  lesser  distance),  from  the  centers  of 
the  six  surrounding  spheres  in  the  same  layer;  and  at  the 
same  distance  from  the  centers  of  the  adjoining  spheres  in 
the  other  and  parallel  layer;  then,  if  planes  of  intersec¬ 
tion  between  the  several  spheres  in  both  layers  be  formed, 
there  will  result  a  double  layer  of  hexagonal  prisms  united 
together  by  pyramidal  bases  formed  of  three  rhombs;  and 
the  rhombs  and  the  sides  of  the  hexagonal  prisms  will  have 


262 


SPECIAL  INSTINCTS . 


every  angle  identically  the  same  with  the  best  measure¬ 
ments  which  have  been  made  of  the  cells  of  the  hive-bee. 
But  I  hear  from  Professor  Wyman,  who  has  made  numer¬ 
ous  careful  measurements,  that  the  accuracy  of  the  work¬ 
manship  of  the  bee  has  been  greatly  exaggerated;  so  much 
so,  that  whatever  the  typical  form  of  the  cell  may  be,  it  is 
rarely,  if  ever,  realized. 

Hence  we  may  safely  conclude  that,  if  we  could  slightly 
modify  the  instincts  already  possessed  by  the  Melipona, 
and  in  themselves  not  very  wonderful,  this  bee  would  make 
a  structure  as  wonderfully  perfect  as  that  of  the  hive-bee. 
We  must  suppose  the  Melipona  to  have  the  power  of  form¬ 
ing  her  cells  truly  spherical,  and  of  equal  sizes;  and  this 
would  not  be  very  surprising,  seeing  that  she  already  does 
so  to  a  certain  extent,  and  seeing  what  perfectly  cylindri¬ 
cal  burrows  many  insects  make  in  wood,  apparently  by 
turning  round  on  a  fixed  point.  We  must  suppose  the 
Melipona  to  arrange  her  cells  in  level  layers,  as  she  already 
does  her  cylindrical  cells;  and  we  must  further  suppose, 
and  this  is  the  greatest  difficulty,  that  she  can  somehow 
judge  accurately  at  what  distance  to  stand  from  her  fellow- 
laborers  when  several  are  making  their  spheres;  but  she  is 
already  so  far  enabled  to  judge  of  distance,  that  she  always 
describes  her  spheres  so  as  to  intersect  to  a  certain  extent; 
and  then  she  unites  the  points  of  intersection  by  perfectly 
flat  surfaces.  By  such  modifications  of  instincts  which  in 
themselves  are  not  very  wonderful — hardly  more  wonderful 
than  those  which  guide  a  bird  to  make  its  nest — I  believe 
that  the  hive-bee  has  acquired,  through  natural  selection, 
her  inimitable  architectural  powers. 

But  this  theory  can  be  tested  by  experiment.  Following 
the  example  of  Mr.  Tegetmeier,  I  separated  two  combs, 
and  put  between  them  a  long,  thick,  rectangular  strip  of 
wax:  the  bees  instantly  began  to  excavate  minute  circular 
pits  in  it;  and  as  they  deepened  these  little  pits,  they  made 
them  wider  and  wider  until  they  were  converted  into 
shallow  basins,  appearing  to  the  eye  perfectly  true  or  parts 
of  a  sphere,  and  of  about  the  diameter  of  a  cell.  It  was 
most  interesting  to  observe  that,  wherever  several  bees  had 
begun  to  excavate  these  basins  near  together,  they  had 
begun  their  work  at  such  a  distance  from  each  other  that 
by  the  time  the  basins  had  acquired  the  above-stated  width 


CELL-MAKING  INSTINCT.  263 

(i.e.  about  the  width  of  an  ordinary  cell),  and  were  in  depth 
about  one-sixth  of  the  diameter  of  the  sphere  of  which  they 
formed  a  part,  the  rims  of  the  basins  intersected  or  broke 
into  each  other.  As  soon  as  this  occurred,  the  bees  ceased 
to  evcavate,  and  began  to  build  up  flat  walls  of  wax  on  the 
lines  of  intersection  between  the  basins,  so  that  each  hexa¬ 
gonal  prism  was  built  upon  the  scalloped  edge  of  a  smooth 
basin,  instead  of  on  the  straight  edges  of  a  three-sided 
pyramid  as  in  the  case  of  ordinary  cells. 

.  ^  then  put  into  the  hive,  instead  of  a  thick,  rectangular 
piece  of  wax,  a  thin  and  narrow,  knife-edged  ridge,  colored 
with  vermilion.  The  bees  instantly  began  on  both  sides 
to  excavate  little  basins  near  to  each  other,  in  the  same 
way  as  before;  but  the  ridge  of  wax  was  so  thin,  that  the 
bottoms  of  the  basins,  if  they  had  been  excavated  to  the 
same  depth  as  in  the  former  experiment,  would  have 
broken  into  each  other  from  the  opposite  sides.  The  bees, 
however,  did  not  suffer  this  to  happen,  and  they  stopped 
their  excavations  in  due  time;  so  that  the  basins,  as  soon 
as  they  had  been  a  little  deepened,  came  to  have  flat  bases; 
and  these  flat  bases,  formed  by  thin  little  plates  of  the  ver¬ 
milion  wax  left  ungnawed,  were  situated,  as  far  as  the  eye 
could  judge,  exactly  along  the  planes  of  imaginary  inter¬ 
section  between  the  basins  on  the  opposite  side  of  the  ridge 
of  wax.  In  some  parts,  only  small  portions,  in  other 
parts,  large  portions  of  a  rhombic  plate  were  thus  left  be¬ 
tween  the  opposed  basins,  but  the  work,  from  the  unnat¬ 
ural  state  of  things,  had  not  been  neatly  performed.  The 
bees  must  have  worked  at  very  nearly  the  same  rate  in 
circularly  gnawing  away  and  deepening  the  basins  on  both 
sides  of  the  ridge  of  vermilion  wax,  in  order  to  have  thus 
succeeded  in  leaving  flat  plates  between  the  basins,  by 
stopping  work  at  the  planes  of  intersection. 

Considering  how  flexible  thin  wax  is,  I  do  not  see  that 
there  is  any  difficulty  in  the  bees,  while  at  work  on  the 
two  sides  of  a  strip  of  wax,  perceiving  when  they  have 
gnawed  the  wax  away  to  the  proper  thinness,  and  then 
stopping  their  work.  In  ordinary  combs  it  has  appeared 
to  me  that  the  bees  do  not  always  succeed  in  working  at 
exactly  the  same  rate  from  the  opposite  sides;  for  I  have 
noticed  half-completed  rhombs  at  the  base  of  a  just  com¬ 
menced  cell,  which  were  slightly  concave  on  one  side. 


264 


SPECIAL  INSTINCTS. 


where  I  suppose  that  the  bees  had  excavated  too  quickly, 
and  convex  on  the  opposed  side  where  the  bees  had  worked 
less  quickly.  In  one  well-marked  instance,  I  put  the  comb 
back  into  the  hive,  and  allowed  the  bees  to  go  on  working 
for  a  short  time,  and  again  examined  the  cell,  and  I  found 
that  the  rhombic  plate  had  been  completed,  and  had 
become  perfectly  flat:  it  was  absolutely  impossible,  from 
the  extreme  thinness  of  the  little  plate,  that  they  could 
have  affected  this  by  gnawing  away  the  convex  side;  and 
I  suspect  that  the  bees  in  such  cases  stand  on  opposite  sides 
and  push  and  bend  the  ductile  and  warm  wax  (which  as  I 
have  tried  is  easily  done)  into  its  proper  intermediate 
plane,  and  thus  flatten  it. 

From  the  experiment  of  the  ridge  of  vermilion  wax  we 
can  see  that,  if  the  bees  were  to  build  for  themselves  a 
thin  wall  of  wax,  they  could  make  their  cells  of  the  proper 
shape,  by  standing  at  the  proper  distance  from  each  other, 
by  excavating  at  the  same  rate,  and  by  endeavoring  to 
make  equal  spherical  hollows,  but  never  allowing  the 
spheres  to  break  into  each  other.  Now  bees,  as  may  be 
clearly  seen  by  examining  the  edge  of  a  growing  comb,  do 
make  a  rough,  circumferential  wall  or  rim  all  round  the 
comb;  and  they  gnaw  this  away  from  the  opposite  sides, 
always  working  circularly  as  they  deepen  each  cell.  They 
do  not  make  the  whole  three-sided  pyramidal  base  of  any 
one  cell  at  the  same  time,  but  only  that  one  rhombic  plate 
which  stands  on  the  extreme  growing  margin,  or  the  two 
plates,  as  the  case  may  be;  and  they  never  complete  the 
upper  edges  of  the  rhombic  plates,  until  the  hexagonal 
walls  are  commenced.  Some  of  these  statements  differ 
from  those  made  by  the  justly  celebrated  elder  Huber,  but 
I  am  convinced  of  their  accuracy;  and  if  I  had  space,  I 
could  show  that  they  are  conformable  with  my  theory. 

Huber  s  statement,  that  the  very  first  cell  is  excavated 
out  of  a  little  parallel-sided  wall  of  wax,  is  not,  as  far  as  I 
have  seen,  strictly  correct;  the  first  commencement  having 
always  been  a  little  hood  of  wax;  but  I  will  not  here  enter 
on  details.  We  see  how  important  a  part  excavation  plays 
in  the  construction  of  the  cells;  but  it  would  be  a  great 
error  to  suppose  that  the  bees  cannot  build  up  a  rough  wall  of 
wax  in  the  proper  position — that  is,  along  the  plane  of  inter¬ 
section  between  two  adjoining  spheres.  I  have  several 


CELL-MAKING  INSTINCT.  261 

epeoimenS  showing  dearly  that  they  can  do  this.  Even 
in  the  rude  circumferential  rim  or  wall  of  wax  round  a 
growing  comb,  flexures  may  sometimes  be  observed  cor¬ 
responding  in  position  to  the  planes  of  the  rhombic  basal 
plates  of  future  cells.  But  the  rough  wall  of  wax  has  h 

one?othSesid°es  Tbfm  °ff>  by  bei?f  W  gnawed  a^ay 
on  noth  sides,  ihe  manner  in  which  the  bees  build  is 

cm  ions;  they  always  make  the  first  rough  wall  from  ten  to 

twenty  times  thicker  than  the  excessively- thin  finished  wall 

standehow  (Wh  'u1  "ltimatelJ  be  left.  We  shall  under¬ 
stand  how  they  work,  by  supposing  masons  first  to  pile  un 

a  broad  ridge  of  cement,  and  then  to  begin  cutting  it  awav 

tC^walMsYff  Slde;s1neai'.  tbe  ground,  till  a  smooth,  very 
nnrt.ri  t  ft  m  the  raiddlei  ‘he  masons  always  piling 

summit  of  thp7  TeDSrd  fdnin?  fresh  ceraent  on  thf 
summit  of  the  ridge.  We  shall  thus  have  a  thin  wall 

steadily  growing  upward  but  always  crowned  by  a  gigantic 

coping.  From  all  the  cells,  both  those  just  commenced 

of  laT°  H  C0£1Pleted’  b.em£  thus  crowned  by  a  strong  coping 
of  wax,  the  bees  can  cluster  and  crawl  over  the  comb  with? 
out  injuring  the  delicate  hexagonal  walls.  These  walls  as 
Professor  Miller  has  kindly  ascertained  for  me,  vary  greatly 
in  thickness;  being,  on  an  average  of  twelve  measure^ 
ments  made  near  the  border  of  the  comb.  toTof  an 
inch  m  thickness;  whereas  the  basal  rhomboidafplates  are 

mian\VTrly  lnethe  ProPOTtion  of  three  to  two, having  a 
mean  thickness,  from  twenty-one  measurements,  of  i  ,g0f 

an  inch..  By  the  above  singular  manner  of  building 
strength  is  continually  given  to  the  comb,  with  the  utmoft 
ultimate  economy  of  wax.  UbC 

It  seems  at  first  to  add  to  the  difficulty  of  understanding 
how  the  cells  are  made,  that  a  multitude  of  bees  alTwwk 

?o!nfccrhfn;  0neti  bee  af?T  workinS  a  short  time  at  one  cell 
to  ,anoth®r’  80  ^at,  as  Huber  has  stated,  a  score  of 
dividuals  work  even  at  the  commencement  of  the  first 

ft!  »d  1  Wa?  fulev  Praotlcall-y  to  sh°w  this  fact,  by  covering 
w  dges  of -the  bexagonal  walls  of  a  single  cell,  or  the  ex“ 
.rerne  margin  of  the  circumferential  rim  of  a  growing 
-omb,  with  an  extremely  thin  layer  of  melted  vermilion 
™tei  1  I“vanably  found  that  the  color  was  most  deli- 

iave  doneTwbb  b'6  bees~as.  delicately  as  a  painter  couid 
ia\e  done  it  with  his  brush— Dy  atoms  of  the  colored  wax 


266 


SPECIAL  INSTINCTS. 


having  been  taken  from  the  spot  on  which  it  had  beea 
placed,  and  worked  into  the  growing  edges  of  the  cells  all 
round.  The  work  of  construction  seems  to  be  a  sort  of 
balance  struck  between  many  bees,  all  instinctively  stand¬ 
ing  at  the  same  relative  distance  from  each  other,  all  trying 
to  sweep  equal  spheres,  and  then  building  up,  or  leaving 
ungnawed,  the  planes  of  intersection  between  these  spheres. 
It  was  really  curious  to  note  in  cases  of  difficulty,  as  when 
two  pieces  of  comb  met  at  an  angle,  how  often  the  bees 
would  pull  down  and  rebuild  in  different  ways  the  same 
cell,  sometimes  recurring  to  a  shape  which  they  had  at  first 
rejected. 

When  bees  have  a  place  on  which  they  can  stand  in  their 
proper  positions  for  working — for  instance,  on  a  slip  of 
wood,  placed  directly  under  the  middle  of  a  comb  growing 
downward,  so  that  the  comb  has  to  be  built  over  one  face 
of  the  slip — in  this  case  the  bees  can  lay  the  foundations  of 
one  wall  of  a  new  hexagon,  in  its  strictly  proper  place, 
projecting  beyond  the  other  completed  cells.  It  suffices 
that  the  bees  should  be  enabled  to  stand  at  their  proper 
relative  distances  from  each  other  and  from  the  walls  of 
the  last  completed  cells,  and  then,  by  striking  imaginary 
spheres,  they  can  build  up  a  wall  intermediate  between  two 
adjoining  spheres;  but  as  far  as  1  have  seen,  they  never 
gnaw  away  and  finish  off  the  angles  of  a  cell  till  a  large  part 
both  of  that  cell  and  of  the  adjoining  cells  has  been  built. 
This  capacity  in  bees  of  laying  down  under  certain  circum¬ 
stances  a  rough  wall  in  its  proper  place  between  two  just 
commenced  cells,  is  important,  as  it  bears  on  a  fact,  which 
seems  at  first  subversive  of  the  foregoing  theory;  namely, 
that  the  cells  on  the  extreme  margin  of  wasp-combs  are 
sometimes  strictly  hexagonal;  but  I  have  not  space  here  to 
enter  on  this  subject.  Nor  does  there  seem  to  me  any 
great  difficulty  in  a  single  insect  (as  in  the  case  of  a  queen- 
wasp)  making  hexagonal  cells,  if  she  were  to  work  alter¬ 
nately  on  the  inside  and  outside  of  two  or  three  cells  com¬ 
menced  at  the  same  time,  always  standing  at  the  proper 
relative  distance  from  the  parts  of  the  cells  just  begun, 
sweeping  spheres  or  cylinders,  and  building  up  interme¬ 
diate  planes. 

As  natural  selection  acts  only  by  the  accumulation  of 
slight  modifications  of  structure  or  instinct,  each  profitable 


CELL-MAKING  INSTINCT.  267 

to  the  individual  under  its  conditions  of  life,  it  may  reason¬ 
ably  be  asked,  how  a  long  and  graduated  succession  of 
modified  architectural  instincts,  all  tending  toward  the  pres¬ 
ent  perfect  plan  of  construction,  could  have  profited  the 
progenitors  of  the  hive-bee?  I  think  the  answer  is  not 
difficult:  cells  constructed  like  those  of  the  bee  or  the  wasp 
gain  in  strength,  and  save  much  in  labor  and  space,  and  in 
the  materials  of  which  they  are  constructed.  With  respect 
to  the  formation  of  wax,  it  is  known  that  bees  are  often 
liaid  pressed  to  get  sufficient  nectar,  and  I  am  informed 
by  Mr.  Tegetmeier  that  it  has  been  experimentally  proved 
that  from  twelve  to  fifteen  pounds  of  dry  sugar  are  con¬ 
sumed  by  a  hive  of  bees  for  the  secretion  of  a  pound  of 
wax;  so  that  a  prodigious  quantity  of  fluid  nectar  must 
be  collected  and  consumed  by  the  bees  in  a  hive  for  the 
secretion  of  the  wax  necessary  for  the  construction  of  their 
combs.  Moreover,  many  bees  have  to  remain  idle  for 
many  days  during  the  process  of  secretion.  A  large 
store  of  honey  is  indispensable  to  support  a  large  stock  of 
bees  during  the  winter;  and  the  security  of  the  hive  is 
known  mainly  to  depend  on  a  large  number  of  bees  being 
supported.  Hence  the  saving  of  wax  by  largely  saving 
honey,  and  the  time  consumed  in  collecting  the  honey, 
must  be  an  important  element  of  success  to  any  family 
of  bees.  Of  course  the  success  of  the  species  may  be  de¬ 
pendent  on  the  number  of  its  enemies,  or  parasites,  or  on 
quite  distinct  causes,  and  so  be  altogether  independent 
of  the  quantity  of  honey  which  the  bees  can  collect.  But 
let  us  suppose  that  this  latter  circumstance  determined,  as 
it  probably  often  has  determined,  whether  a  bee  allied 
to  our  humble-bees  could  exist  in  large  numbers  in  any 
countiy;  and  let  us  further  suppose  that  the  community 
lived  through  the  winter,  and  consequently  required  a  store 
of  honey:  there  can  in  this  case  be  no  doubt  that  it  would 
be  an  advantage  to  our  imaginary  humble-bee  if  a  slight 
modification  in  her  instincts  led  her  to  make  her  waxen 
cells  near  together,  so  as  to  intersect  a  little;  for  a  wall  in 
common  even  to  two  adjoining  cells  would  save  some  little 
labor  and  wax.  Hence,  it  would  continually  be  more  and 
moi  e  ad\antageous  to  our  humble  bees,  if  they  were  to 
make  their  cells  more  and  more  regular,  nearer  together, 
and  aggregated  into  a  mass,  like  the  cells  of  the  Melipona; 


OBJECTIONS  TO  THE  THEORY 


268 

for  in  this  case  a  large  part  of  the  bounding  surface  of  each 
cell  would  serve  to  bound  the  adjoining  cells,  and  much 
labor  and  wax  would  be  saved.  Again,  from  the  same 
cause,  it  would  be  advantageous  to  the  Melipona,  if  she 
were  to  make  her  cells  closer  together,  and  more  regular 
in  every  way  than  at  present;  for  then,  as  we  have  seen, 
the  spherical  surfaces  would  wholly  disappear  and  be  re¬ 
placed  by  plane  surfaces;  and  the  Melipona  would  make  a 
comb  as  perfect  as  that  of  the  hive-bee.  Beyond  this  stage 
of  perfection  in  architecture,  natural  selection  could  not 
lead;  for  the  comb  of  the  liive-bee,  as  far  as  we  can  see,  is 
absolutely  perfect  in  economizing  labor  and  wax. 

Thus,  as  I  believe,  the  most  wonderful  of  all  known  in¬ 
stincts,  that  of  the  hive-bee,  can  be  explained  by  natural 
selection  having  taken  advantage  of  numerous,  successive, 
slight  modifications  of  simpler  instincts;  natural  selection 
having,  by  slow  degrees,  more  and  more  perfectly  led  the 
bees  to  sweep  equal  spheres  at  a  given  distance  from  each 
other  in  a  double  layer,  and  to  build  up  and  excavate  the 
wax  along  the  planes  of  intersection;  the  bees,  of  course, 
no  more  knowing  that  they  swept  their  spheres  at  one  par¬ 
ticular  distance  from  each  other,  than  they  know  what  are 
the  several  angles  of  the  hexagonal  prisms  and  of  the  basal 
rhombic  plates;  the  motive  power  of  the  process  of  natural 
selection  having  been  the  construction  of  cells  of  duo 
strength  and  of  the  proper  size  and  shape  for  the  larvae, 
this  being  effected  with  the  greatest  possible  economy  of 
labor  and  wax;  that  individual  swarm  which  thus  made 
the  best  cells  with  least  labor,  and  least  waste  of  honey  in 
the  secretion  of  wax,  having  succeeded  best,  and  having 
transmitted  their  newly-acquired  economical  instincts  to 
new  swarms,  which  in  their  turn  will  have  had  the  best 
chance  of  succeeding  in  the  struggle  for  existence. 

OBJECTIONS  TO  THE  THEORY  OP  NATURAL  SELECTION  AS 

APPLIED  TO  INSTINCTS!  NEUTER  AND  STERILE  INSECTS. 

It  has  been  objected  to  the  foregoing  view  of^  the  origin 
of  instincts  that  “  the  variations  of  structure  and  of  instinct 
must  have  been  simultaneous  and  accurately  adjusted  to  each 
other,  as  a  modification  in  the  one  without  an  immediate 
corresponding  change  in  the  other  would  have  been  fatal.” 


OF  NATURAL  SELECTION.  269 

The  force  of  this  objection  rests  entirely  on  the  assumption 
that  the  changes  in  the  instincts  and  structure  are  abrupt, 
lo  take  as  an  illustration  the  case  of  the  larger  titmouse, 
(Parus  major)  alluded  to  in  a  previous  chapter;  this  bird 
often  holds  the  seeds  of  the  yew  between  its  feet  on  a 
branch,  and  hammers  with  its  beak  till  it  gets  at  the 
kernel.  Now  what  special  difficulty  would  there  be  in  natu¬ 
ral  selection  preserving  all  the  slight  individual  variations 
m  the  shape  of  the  beak,  which  were  better  and  better 
adapted  to  break  ojoen  the  seeds,  until  a  beak  was  formed, 
as  well  constructed  for  this  purpose  as  that  of  the  nut¬ 
hatch,  at  the  same  time  that  habit,  or  compulsion,  or 
spontaneous  variations  of  taste,  led  the  bird  to  become 
more  and  more  of  a  seed-eater?  In  this  case  the  beak  is 
supposed  to  be  slowly  modified  by  natural  selection,  subse¬ 
quently  to,  but  in  accordance  with,  slowly  changing  habits 
or  taste;  but  let  the  feet  of  the  titmouse  vary  and  grow 
larger  from  correlation  with  the  beak,  or  from  any  other 
unknown  cause,  and  it  is  not  improbable  that  such  larger 
feet  would  lead  the  bird  to  climb  more  and  more  until  it 
acquiied  the  remarkable  climbing  instinct  and  power  of 
the  nuthatch.  In  this  case  a  gradual  change  of  structure 
is  supposed  to  lead  to  changed  instinctive  habits.  To  take 
one  more  case:  few  instincts  are  more  remarkable  than  that 
which  leads  the  swift  of  the  Eastern  Islands  to  make  its 
nest  wholly  of  inspissated  saliva.  Some  birds  build  their 
nests  of  mud,  believed  to  be  moistened  with  saliva;  and 
one  of  the  swifts  of  North  America  makes  its  nest  (as  I 
have  seen)  of  sticks  agglutinated  with  saliva,  and  even  with 
flakes  of  this  substance.  .  Is  it  then  very  improbable  that 
the  natuial  selection  of  individual  swifts,  which  secreted 
more  and  more  saliva,  should  at  last  produce  a  species  with 
instincts  leading  it  to  neglect  other  materials  and  to  make 
its  nest  exclusively  of  inspissated  saliva?  And  so  in  other 
cases.  It  must,  however,  be  admitted  that  in  many 
instances  we  cannot  conjecture  whether  it  was  instinct  or 
structure  which  first  varied. 

No  doubt  many  instincts  of  very  difficult  explanation 
could  be  opposed  to  the  theory  of  natural  selection — cases, 
in  which  we  cannot  see  how  an  instinct  could  have  origin¬ 
ated;^  cases,  in  which  no  intermediate  gradations  are  known 
to  exist;  cases  of  instincts  of  such  trifling  importance,  that 


270  OBJECTIONS  TO  THE  THEORY 

they  could  hardly  have  been  acted  on  by  natural  selection; 
cases  of  instincts  almost  identically  the  same  in  animals  so 
remote  in  the  scale  of  nature  that  we  cannot  account,  foi 
their  similarity  by  inheritance  from  a  common  progenitor, 
and  consequently  must  believe  that  they  were  independ¬ 
ently  acquired  through  natural  selection.  I  will  not  here 
enter  on  these  several  cases,  but  will  confine  myself  to  one 
special  difficulty,  which  at  first  appeared  tome  insuperable, 
and  actually  fatal  to  the  whole  theory.  I  allude  to  the 
neuters  or  sterile  females  in  insect  communities;  for  these 
neuters  often  differ  widely  in  instinct  and  in  structure  from 
both  the  males  and  fertile  females,  and  yet,  from  being 
sterile,  they  cannot  propagate  their  kind. 

The  subject  well  deserves  to  be  discussed  at  great  length, 
but  I  will  here  take  only  a  single  case,  that  of  working  or 
sterile  ants.  How  the  workers  have  been  rendered  sterile 
is  a  difficulty;  but  not  much  greater  than  that  of  any 
other  striking  modification  of  structure;,  for  it  can  be 
shown  that  some  insects  and  other  articulate  animals 
in  a  state  of  nature  occasionally  become  sterile;  and  if 
such  insects  had  been  social,  and  it  had  been  profitable 
to  the  community  that  a  number  should  have  been 
annually  born  capable  of  work,  but  incapable  of  procrea¬ 
tion,  I  can  see  no  especial  difficulty  in  this  having  been 
effected  through  natural  selection.  But  I  must  passover 
this  preliminary  difficulty.  The  great  difficulty  lies  in 
the  working  ants  differing  widely  from  both  the  males 
and  the  fertile  females  in  structure,  as  in  the  shape 
of  the  thorax,  and  in  being  destitute  of  wings  and  some¬ 
times  of  eyes,  and  in  instinct.  As  far  as.  instinct 
alone  is  concerned,  the  wonderful  difference  in  this  lespect 
between  the  workers  and  the  perfect  females  would  have 
been  better  exemplified  by  the  hive-bee.  If  a  working  ant 
or  other  neuter  insect  had  been  an  ordinary  animal,  I 
should  have  unhesitatingly  assumed  that  all  its  characters 
had  been  slowly  acquired  through  natural .  selection; 
namely,  by  individuals  having  been  born  with  slight  profit¬ 
able  modifications,  which  were  inherited  by  the  offspring, 
and  that  these  again  varied  and  again  were  selected,  and  so 
onward.  But  with  the  working  ant  we  have  an  insect 
differing  greatly  from  its  parents,  yet  absolutely  sterile.;  so 
that  it  could  never  have  transmitted  successively  acquired 


OF  NA  TURAL  SELECTION. 


271 

modifications  of  structure  or  instinct  to  its  progeny.  It 
may  well  be  asked  how  it  is  possible  to  reconcile  this  case 
with  the  theory  of  natural  selection? 

hirst,  let  it  be  remembered  that  we  have  innumerable  in¬ 
stances,  both  in  our  domestic  productions  and  in  those  in 
a  state  of  nature,  of  all  sorts  of  differences  of  inherited 
structure  which  are  correlated  with  certain  ages  and  with 
either  sex.  We  have  differences  correlated  not  only  with 
one  sex,  but  with  that  short  period  when  the  reproductive 
system  is  active,  as  in  the  nuptial  plumage  of  many  birds, 
and  in  the  hooked  jaws  of  the  male  salmon.  We  have  even 
slight  differences  in  the  horns  of  different  breeds  of  cattle 
in  relation  to  an  artificially  imperfect  state  of  the  male 
sex,  for  oxen  of  certain  breeds  have  longer  horns  than  the 
oxen  of  other  breeds,  relatively  to  the  length  of  the  horns 
in  both  the  bulls  and  cows  of  these  same  breeds.  Hence, 
I  can  see  no  great  difficulty  in  any  character  becoming  cor¬ 
related  with  the  sterile  condition  of  certain  members  of 
insect  communities;  the  difficulty  lies  in  understanding 
how  such  correlated  modifications  of  structure  could  have 
been  slowly  accumulated  by  natural  selection. 

This  difficulty,  though  _  appearing  insuperable,  is 
lessened,  or,  as  I  believe,  disappears,  when  it  is  remem¬ 
bered  that  selection  may  be  applied  to  the  family,  as  well 
as  to  the  individual,  and  may  thus  gain  the  desired  end. 
Breeders  of  cattle  wish  the  flesh  and  fat  to  be  well  marbled 
together.  An  animal  thus  characterized  has  been  slaugh¬ 
tered,  but  the  breeder  has  gone  with  confidence  to  the 
same  stock  and  has  succeeded.  Such  faith  may  be  placed  in 
the  power  of  selection  that  a  breed  of  cattle,  always  yield¬ 
ing  oxen  with  extraordinarily  long  horns,  could,  it  is  prob¬ 
able,  be  formed  by  carefully  watching  which  individual 
bulls  and  cows,  when  matched,  produced  oxen  with  the 
longest  horns;  and  yet  no  one  ox  would  ever  have  propa¬ 
gated  its  kind.  Here  is  a  better  and  real  illustration: 
According  to  M.  Verlot,  some  varieties  of  the  double 
annual  stock,  from  having  been  long  and  carefully  selected 
to  the  right  degree,  always  produce  a  large  proportion  of 
seedlings  bearing  double  and  quite  sterile  flowers,  but  they 
likewise  yield  some  single  and  fertile  plants.  These  latter, 
by  which  alone  the  variety  can  be  propagated,  may  be 
compared  with  the  fertile  male  and  female  ants,  and  the 


272 


OBJECTIONS  TO  THE  THEORY 


double  sterile  plants  with,  the  neuters  of  the  same  com¬ 
munity.  As  with  the  varieties  of  the  stock,  so  with  social 
insects,  selection  has  been  applied  to  the  family,  and  not 
to  the  individual,  for  the  sake  of  gaining  a  serviceable  end. 
Hence,  we  may  conclude  that  slight  modifications  of 
structure  or  of  instinct,  correlated  with  the  sterile  condi¬ 
tion  of  certain  members  of  the  community,  have  proved 
advantageous;  consequently  the  fertile  males  and  females 
have  flourished,  and  transmitted  to  their  fertile  offspring  a 
tendency  to  produce  sterile  members  with  the  same  modifi¬ 
cations.  This  process  must  have  been  repeated  many 
times,  until  that  prodigious  amount  of  difference  between 
the  fertile  and  sterile  females  of  the  same  species  has  been 
produced  which  we  see  in  many  social  insects. 

But  we  have  not  as  yet  touched  on  the  acme  of  the  dif¬ 
ficulty;  namely,  the  fact  that  the  neuters  of  several  ants 
differ,  not  only  from  the  fertile  females  and  _  males,  but 
from  each  other,  sometimes  to  an  almost  incredible  degree, 
and  are  thus  divided  into  two  or  even  three  castes.  The 
castes,  moreover,  do  not  commonly  graduate  into  each 
other,  but  are  perfectly  well  defined;  being  as  distinct  from 
each  other  as  are  any  two  species  of  the  same  genus,  or 
rather  as  any  two  genera  of  the  same  family.  Thus,  in 
Eciton,  there  are  working  and  soldier  neuters,  with  jaws 
and  instincts  extraordinarily  different:  in  Cryptocerus,  the 
workers  of  one  caste  alone  carry  a  wonderful  sort  of  shield 
on  their  heads,  the  use  of  which  is  quite  unknown;  in  the 
Mexican  Myrmecocystus,  the  workers  of  one  caste  never 
leave  the  nest;  they  are  fed  by  the  workers  of  another 
caste,  and  they  have  an  enormously  developed  abdomen 
which  secretes  a  sort  of  honey,  supplying  the  place  of  that 
excreted  by  the  aphides,  or  the  domestic  cattle  as  they  may 
be  called,  which  our  European  ants  guard  and  imprison. 

It  will  indeed  be  thought  that  I  have  an  overweening 
confidence  in  the  principle  of  natural  selection,  when  I  do 
not  admit  that  such  wonderful  and  well-established  facts 
at  once  annihilate  the  theory.  In  the  simpler  case  of 
neuter  insects  all  of  one  caste,  which,  as  I  believe,  have 
been  rendered  different  from  the  fertile  males  and  females 
through  natural  selection,  we  may  conclude  from  _  the 
analogy  of  ordinary  variations,  that  the  successive,  slight, 
profitable  modifications  did  not  first  arise  in  all  the  neuters 


OF  NATURAL  SELECTION 


273 


in  the  same  nest,  but  in  some  few  alone;  and  that  by  the 
survival  of  the  communities  with  females  which  produced 
most  neuters  having  the  advantageous  modification,  all 
the  neuters  ultimately  came  to  be  thus  characterized.  Ac¬ 
cording  to  this  view  we  ought  occasionally  to  find  in  the 
same  nest  neuter  insects,  presenting  gradations  of  struct¬ 
ure;  and  this  we  do  find,  even  not  rarely,  considering  how 
few  neuter  insects  out  of  Europe  have  been  carefully  ex¬ 
amined.  Mr.  F.  Smith  has  shown  that  the  neuters  of 
several  British  ants  differ  surprisingly  from  each  other  in 
size  and  sometimes  in  color;  and  that  the  extreme  forms  can 
be  linked  together  by  individuals  taken  out  of  the  same  nest: 
I  have  myself  compared  perfect  gradations  of  this  kind. 
It  sometimes  happens  that  the  larger  or  the  smaller  sized 
workers  are  the  most  numerous;  or  that  both  large  and 
small  are  numerous,  while  those  of  an  intermediate  size 
are  scanty  in  numbers.  Formica  flava  has  larger  and 
smaller  workers,  with  some  few  of  intermediate  size;  and, 
in  this  species,  as  Mr.  F.  Smith  has  observed,  the  larger 
workers  have  simple  eyes  (ocelli),  which,  though  small,  can 
be  plainly  distinguished,  whereas  the  smaller  workers  have 
their  ocelli  rudimentary.  Having  carefully  dissected 
several  specimens  of  these  workers,  I  can  affirm  that  the 
eyes  are  far  more  rudimentary  in  the  smaller  workers  than 
can  be  accounted  for  merely  by  their  proportionately  lesser 
size;  and  I  fully  believe,  though  I  dare  not  assert  so  posi¬ 
tively,  that  the  "workers  of  intermediate  size  have  their 
ocelli  in  an  exactly  intermediate  condition.  So  that  here 
we  have  two  bodies  of  sterile  workers  in  the  same  nest,  dif¬ 
fering  not  only  in  size,  but  in  their  organs  of  vision,  yet 
connected  by  some  few  members  in  an  intermediate 
condition.  I  may  digress  by  adding,  that  if  the  smaller 
workers  had  been  the  most  useful  to  the  community,  and 
those  males  and  females  had  been  continuallv  selected, 
which  produced  more  and  more  of  the  smaller  workers, 
until  all  the  workers  were  in  this  condition,  we  should 
then  have  had  a  species  of  ant  with  neuters  in  nearly  the 
same  condition  as  those  of  Myrmica.  For  the  workers  of 
Myrmicahave  not  even  rudiments  of  ocelli,  though  the  male 
and  female  ants  of  this  genus  have  well-developed  ocelli. 

I  may  give  one  other  case:  so  confidently  did  I  expect 
occasionally  to  find  gradations  of  important  structures 


274 


OBJECTIONS  TO  THE  THEORY 


between  the  different  castes  of  neuters  in  the  same  species, 
that  I  gladly  availed  myself  of  Mr.  F.  Smith's  offer  of 
numerous  specimens  from  the  same  nest  of  the  driver  ant 
(Anomma)  of  West  Africa.  The  reader  will  perhaps  best 
appreciate  the  amount  of  difference  in  these  workers  by 
my  giving,  not  the  actual  measurements,  but  a  strictly 
accurate  illustration:  the  difference  was  the  same  as  if  we 
were  to  see  a  set  of  workmen  building  a  house,  of  whom 
many  were  five  feet  four  inches  high,  and  many  sixteen  feet 
high;  but  we  must  in  addition  suppose  that  the  larger 
workmen  had  heads  four  instead  of  three  times  as  big  as 
those  of  the  smaller  men,  and  jaws  nearly  five  times  as  big. 
The  jaws,  moreover,  of  the  working  ants  of  the  several 
sizes  differed  wonderfully  in  shape,  and  in  the  form  and 
number  of  the  teeth.  But  the '  important  fact  for  usis 
that,  though  the  workers  can  be  grouped  into  castes  of  dif¬ 
ferent  sizes,  yet  they  graduate  insensibly  into  each  other, 
as  does  the  widely  different  structure  of  their  jaws.  I  speak 
confidently  on  this  latter  point,  as  Sir  J.  Lubbock  made 
drawings  for  me,  with  the  camera  lucida,  o*  the  jaws  which 
I  dissected  from  the  workers  of  the  several  sizes.  Mr. 
Bates,  in  his  interesting  “Naturalist  on  the  A.mazons,” 
has  described  analogous  cases. 

With  these  facts  before  me,  I  believe  that  natural  selec¬ 
tion,  by  acting  on  the  fertile  ants  or  parents,  could  form  a 
species" which  should  regularly  produce  neuters,  all  of  large 
size  with  one  form  of  jaw,  or  all  of  small  size  with  widely 
different  jaws;  or  lastly,  and  this  is  the  greatest  difficulty, 
one  set  of  workers  of  one  size  and  structure,  and  simulta¬ 
neously  another  set  of  workers  of  a  different  size  and 
structure;  a  graduated  series  having  first  been  formed,  as 
in  the  case  of  the  driver  ant,  and  then  the  extreme  forms 
having  been  produced  in  greater  and  greater  numbers, 
through  the  survival  of  the  parents  which  generated  them, 
until  none  with  an  intermediate  structure  were  produced. 

An  analogous  explanation  has  been  given  by  Mr.  Wallace, 
of  the  equally  complex  case,  of  certain  Malayan  butterflies 
regularly  appearing  under  two  or  even  three  distinct 
female  forms;  and  by  Fritz  Muller,  of  certain  Brazilian 
crustaceans  likewise  appearing  under  two  widely  distinct 
male  forms.  But  this  subject  need  not  here  be  discussed. 

I  have  now  explained  how,  I  believe,  the  wTonderful  fact- 


SUMMARY. 


m 

of  two  distinctly  defined  castes  of  sterile  workers  existing 
in  the  same  nest,  both  widely  different  from  each  other 
and  from  their  parents,  has  originated.  We  can  see  how 
useful  their  production  may  haT7e  been  to  a  social  commu¬ 
nity  of  ants,  on  the  same  principle  that  the  division  of 
labor  is  useful  to  civilized  man.  Ants,  however,  work  by 
inherited  instincts  and  by  inherited  organs  or  tools’, 
while  man  works  by  acquired  knowledge  and  manufactured 
instruments.  But  I  must  confess,  that,  with  all  my  faith 
in  natural  selection,  I  should  never  have  anticipated  that 
this  principle  could  have  been  efficient  in  so  high  a  degree, 
had  pot  the  case  of  these  neuter  insects  led  me  to  this"con- 
clusion.  I  have,  therefore,  discussed  this  case,  at  some 
little  but  wholly  insufficient  length,  in  order  to  show  the 
power  of  natural  selection,  and  likewise  because  this  is  by 
far  the  most  serious  special  difficulty  which  my  theory  has 
encountered.  .  The  case,  also,  is  very  interesting,  as  it 
proves  that  with  animals,  as  with  plants,  any  amount  of 
modification  may  be  effected  by  the  accumulation  of 
numerous,  slight,  spontaneous  variations,  which  are  in  any 
way  profitable,  without  exercise  or  habit  having  been 
brought  into  play.  For  peculiar  habits,  confined  to  the 
workers  of  sterile  females,  however  long  they  might  be  fol¬ 
lowed,  could  not  possibly  affect  the  males  and  fertile 
females,  which  alone  leave  descendants.  I  am  surprised 
that  no  one  has  hitherto  advanced  this  demonstrative  case 
of  neuter  insects,  against  the  well-known  doctrine  of  in¬ 
herited  habit,  as  advanced  by  Lamarck. 

SUMMARY. 

I  have  endeavored  in  this  chapter  briefly  to  show  that 
the  mental  qualities  of  our  domestic  animals  vary,  and  that 
the  variations  are  inherited.  Still  more  briefly  I  have  at¬ 
tempted  to  show  that  instincts  vary  slightly  in  a  state  of 
nature.  No  one  will  dispute  that  instincts  are  of  the  high¬ 
est  importance  to  each  animal.  Therefore,  there  is  no  real 
difficulty,  under  changing  conditions  of  life,  in  natural 
selection  accumulating  to  any  extent  slight  modifications 
of  instinct  which  are  in  any  way  useful.  In  many  cases 
habit  or  use  and  disuse  have  probably  come  into  play.  I 
do  not  pretend  that  the  facts  given  in  this  chapter 


SUMMARY. 


276 

strengthen  in  any  great  degree  my  theory;  but  none  of  the 
cases  of  difficulty,  to  the  best  of  my  judgment,  annihilate 
it.  On  the  other  hand,  the  fact  that  instincts  are  not 
always  absolutely  perfect  and  are  liable  to  mistakes;  that 
no  instinct  can  be  shown  to  have  been  produced  for  the 
good  of  other  animals,  though  animals  take  advantage  of 
the  instincts  of  others;  that  the  canon  in  natural  history 
of  (e  Natura  non  facit  saltum,”  is  applicable  to  instincts  as 
well  as  to  corporeal  structure,  and  is  plainly  explicable  on 
the  foregoing  views,  but  is  otherwise  inexplicable — all  tend 
to  corroborate  the  theory  of  natural  selection. 

This  theory  is  also  strengthened  by  some  few  other  facts 
in  regard  to  instincts;  as  by  that  common  case  of  closely 
allied,  but  distinct,  species,  when  inhabiting  distant  parts 
of  the  world  and  living  under  considerable  different  con¬ 
ditions  of  life,  yet  often  retaining  nearly  the  same  instincts. 
For  instance,  we  can  understand,  on  the  principle  of  in¬ 
heritance,  how  it  is  that  the  thrush  of  tropical  South  Amer¬ 
ica  lines  its  nest  with  mud,  in  the  same  peculiar  manner  as 
does  our  British  thrush;  how  it  is  that  the  Hornbills  of 
Africa  and  India  have  the  same  extraordinary  instinct  of 
plastering  up  and  imprisoning  the  females  in  a  hole  in  a 
tree,  with  only  a  small  hole  left  in  the  plaster  through 
which  the  males  feed  them  and  their  young  when  hatched; 
how  it  is  that  the  male  wrens  (Troglodytes)  of  Aorth 
America  build  “  cock-nests,”  to  roost  in,  like  the  males  of 
our  Kitty-wrens — a  habit  wholly  unlike  that  of  any  other 
known  bird.  Finally,  it  may  not  be  a  logical  deduction, 
but  to  my  imagination  it  is  far  more  satisfactory  to  look  at 
such  instincts  as  the  young  cuckoo  ejecting  its  foster- 
brothers,  ants  making  slaves,  the  larvae  of  ichneumonidae 
feeding  within  the  live  bodies  of  caterpillars,  not  as  spe¬ 
cially  endowed  or  created  instincts,  but  as  small  conse¬ 
quences  of  one  general  law  leading  to  the  advancement  of 
all  organic  beings — namely,  multiply,  vary,  let  the  strong* 
*»t  live  and  the  weakest  die. 


HYBRIDISM. 


m 


CHAPTER  IX. 

HYBKIDISM. 

Distinction  between  tbe  sterility  of  first  crosses  and  of  hybrids— 
Sterility  various  in  degree,  not  universal,  affected  by  close  inter¬ 
breeding,  removed  by  domestication  —  Laws  governing  tbe 
sterility  of  hybrids — Sterility  not  a  special  endowment,  but  inci¬ 
dental  on  other  differences,  not  accumulated  by  natural  selec¬ 
tion — Causes  of  the  sterility  of  first  crosses  and  of  hybrids — 
Parallelism  between  the  effects  of  changed  conditions  of  life  and 
of  crossing — Dimorphism  and  trimorphism — Fertility  of  varieties 
when  crossed  and  of  their  mongrel  offspring  not  universal — • 
Hybrids  and  mongrels  compared  independently  of  their  fertility 
• — Summary. 

The  view  commonly  entertained  by  naturalists  is  that 
species,  when  intercrossed,  have  been  specially  endowed 
with  sterlility,  in  order  to  prevent  their  confusion.  This 
view  certainly  seems  at  first  highly  probable,  for  species 
living  together  could  hardly  have  been  kept  distinct  had 
they  been  capable  of  freely  crossing.  The  subject  is  in 
many  ways  important  for  us,  more  especially  as  the  sterility 
of  species  when  first  crossed,  and  that  of  their  hybrid  off¬ 
spring,  cannot  have  been  acquired,  as  I  shall  show,  by  the 
preservation  of  successive  profitable  degrees  of  sterility. 
It  is  an  incidental  result  of  differences  in  the  reproductive 
systems  of  the  parent-species. 

In  treating  this  subject,  two  classes  of  facts,  to  a  large 
extent  fundamentally  different,  have  generally  been  con¬ 
founded;  namely,  the  sterility  of  species  when  first  crossed, 
and  the  sterility  of  the  hybrids  produced  from  them. 

Pure  species  have  of  course  their  organs  of  reproduction 
in  a  perfect  condition,  yet  when  intercrossed  they  produce 
either  few  or  no  offspring.  Hybrids,  on  the  other  hand, 
have  their  reproductive  organs  functionally  impotent,  as 
may  be  clearly  seen  in  the  state  of  the  male  element  in 
both  plants  and  animals;  though  the  formative  organs 


278 


HYBRIDISM. 


themselves  are  perfect  in  structure,  as  far  as  the  micro¬ 
scope  reveals.  In  the  first  case  the  two  sexual  elements 
which  go  to  form  the  embryo  are  perfect;  in  the  second 
case  they  are  either  not  at  all  developed,  or  are  imperfectly 
developed.  This  distinction  is  important,  when  the  cause 
of  the  sterility,  which  is  common  to  the  two  cases,  has  to 
be  considered.  The  distinction  probably  has  been  sluried 
over,  owing  to  the  sterility  in  both  cases  being  looked  on 
as  a  special  endowment,  beyond  the  province  of  our  reason¬ 
ing  powers. 

The  fertility  of  varieties,  that  is  of  the  forms  known  or 
believed  to  be  descended  from  common  parents,  when 
crossed,  and  likewise  the  fertility  of  their  mongrel  off¬ 
spring,  is,  with  reference  to  my  theory,  of  equal  importance 
with  the  sterility  of  species;  for  it  seems  to  make  a  broad 
and  clear  distinction  between  varieties  and  species. 

DEGREES  OF  STERILITY. 

First,  for  the  sterility  of  species  when  crossed  and  of 
their  hybrid  offspring.  ‘  It  is  impossible  to  study  the  sev¬ 
eral  memoirs  and  works  of  those  two  conscientious  and  ad¬ 
mirable  observers,  Kolreuter  and  Gartner,  who  almost 
devoted  their  lives  to  this  subject,  without  being  deeply 
impressed  with  the  high  generality  of  some  degree  of  stei- 
ility.  Kolreuter  makes  the  rule  universal;  but  then  he 
cuts  the  knot,  for  in  ten  cases  in  which  he  found  two  forms, 
considered  by  most  authors  as  distinct  species,  quite  fertile 
together,  he  unhesitatingly  ranks  them  as  varieties.  .  Giiit- 
ner,  also,  makes  the  rule  equally  universal;  and  he  disputes 
the  entire  fertility  of  Kolreuter’s  ten  cases.  But  in  these 
and  in  many  other  cases,  Gartner  is  obliged  carefully  to 
count  the  seeds,  in  order  to  show  that  there  is  any  degiee 
of  sterility.  He  always  compares  the  maximum  number 
of  seeds  produced  by  two  species  when  first  crossed,  and 
the  maximum  produced  by  their  hybrid  offspring,  with 
the  average  number  produced  by  both  pure  parent-species 
in  a  state°of  nature.  But  causes  of  serious  error  here  in¬ 
tervene!  a  plant,  to  be  hybridized,  must  be  castrated,  and, 
what  is  often  more  important,  must  be  secluded  in  order 
to  prevent  pollen  being  brought  to  it  by  insects  from  other 
plants.  Nearly  all  the  plants  experimented  on  by  Gartner 


DEGREES  OF  STERILITY. 


279 


were  potted,  and  were  kept  in  a  chamber  in  his  house. 
That  these  processes  are  often  injurious  to  the  fertility  of 
a  plant  cannot  be  doubted;  for  Gartner  gives  in  his  table 
about  a  score  of  cases  of  plants  which  he  castrated,  and 
artificially  fertilized  with  their  own  pollen,  and  (excluding 
all  cases  such  as  the  Leguminosse,  in  which  there  is  an 
acknowledged  difficulty  in  the  manipulation)  half  of  these 
twenty  plants  had  their  fertility  in  some  degree  impaired. 
Moreover,  as  Gartner  repeatedly  crossed  some  forms,  such 
as  the  common  red  and  blue  pimpernels  (Anagallis  arvensis 
and  coerulea),  which  the  best  botanists  rank  as  varieties, 
and  found  them  absolutely  sterile,  we  may  doubt  whether 
many  species  are  really  so  sterile,  when  intercrossed,  as  he 
believed. 

It  is  certain,  on  the  one  hand,  that  the  sterility  of 
various  species  when  crossed  is  so  different  in  degree  and 
graduates  away  so  insensibly,  and,  on  the  other  hand,  that 
the  fertility  of  pure  species  is  so  easily  affected  by  various 
circumstances,  that  for  all  practical  purposes  it  is  most 
difficult  to  say  where  perfect  fertility  ends  and  sterility 
begins.  I  think  no  better  evidence  of  this  can  be  required 
than  that  the  two  most  experienced  observers  who  have 
ever  lived,  namely  Kolreuter  and  Gartner,  arrived  at 
diametrically  opposite  conclusions  in  regard  to  some  of  the 
very  same  forms.  It  is  also  most  instructive  to  compare — 
but  I  have  not  space  here  to  enter  on  details — the  evidence 
advanced  by  our  best  botanists  on  the  question  whether 
certain  doubtful  forms  should  be  ranked  as  species  or 
varieties,  with  the  evidence  from  fertility  adduced  by  dif¬ 
ferent  hybridizers,  or  by  the  same  observer  from  experi¬ 
ments  made  during  different  years.  It  can  thus  be  shown 
that  neither  sterility  nor  fertility  affords  any  certain  dis¬ 
tinction  between  species  and  varieties.  The  evidence 
from  this  source  graduates  away,  and  is  doubtful  in  the 
same  degree  as  is  the  evidence  derived  from  other  consti¬ 
tutional  and  structural  differences. 

>  In  regard  to  the  sterility  of  hybrids  in  successive  genera¬ 
tions;  though  Gartner  was  enabled  to  rear  some  hybrids, 
carefully  guarding  them  from  a  cross  with  either  pure 
parent,  for  six  or  seven,  and  in  one  case  for  ten  generations, 
yet  he  asserts  positively  that  their  fertility  never  increases, 
but  generally  decreases  greatly  and  suddenly.  With  re- 


HYBRIDISM ; 


280 

spect  to  this  decrease,  it  may  first  be  noticed  that  when 
any  deviation  in  structure  or  constitution  is  common  to 
both  parents,  this  is  often  transmitted  in  an  augmented 
degree  to  the  offspring;  and  both  sexual  elements  in  hybrid 
plants  are  already  affected  in  some  degree.  But  I  believe 
that  their  fertility  has  been  diminished  in  nearly  all  these 
cases  by  an  independent  cause,  namely,  by  too  close  inter¬ 
breeding.  I  have  made  so  many  experiments  and  collected 
so  many  facts,  showing  on  the  one  hand  that  an  occasional 
cross  with  a  distinct  individual  or  variety  increases  the 
vigor  and  fertility  of  the  offspring,  and  on  the  other  hand 
that  very  close  interbreeding  lessens  their  vigor  and  fertil¬ 
ity,  that  I  can  not  doubt  the  correctness  of  this  conclusion. 
Hybrids  are  seldom  raised  by  experimentalists  in  great 
numbers;  and  as  the  parent-species,  or  other  allied  hybrids, 
o-ene rally  grow  in  the  same  garden,  the  visits,  of  insects 
must  be  carefully  prevented  during  the  flowering  season: 
hence  hybrids,  if  left  to  themselves,  will  generally  be  fer¬ 
tilized  during  each  generation  by  pollen  from  the  same 
flower;  and  this  would  probably  be  injurious  to  their  fertil¬ 
ity,  already  lessened  by  their  hybrid  origin.  I  am 
strengthened  in  this  conviction  by  a  remarkable  statement 
repeatedly  made  by  Gartner,  namely,  that  if  even  the  less 
fertile  hybrids  be  artificially  fertilized  with  hybrid  pollen 
of  the  same  kind,  their  fertility,  notwithstanding  the  fre¬ 
quent  ill  effects  from  manipulation,  sometimes  decidedly 
increases,  and  goes  on  increasing.  Now,  in  the  process  of 
artificial  fertilization,  pollen  is  as  often  taken  by  chance 
(as  I  know  from  my  own  experience)  from  the  anthers  of 
another  flower,  as  from  the  anthers  of  the  flower  itself 
which  is  to  be  fertilized;  so  that  a  cross  between  two  flow¬ 
ers,  though  probably  often  on  the  same  plant,  would  be 
thus  effected.  Moreover,  whenever  complicated  experi¬ 
ments  are  in  progress,  so  careful  an  observer  as  Gartner 
would  have  castrated  his  hybrids,  and  this  would  have  in¬ 
sured  in  each  generation  a  cross  with  pollen  from  a  dis¬ 
tinct  flower,  either  from  the  same  plant  or  from  another 
plant  of  the  same  hybrid  nature.  And  thus,  the  strange 
fact  of  an  increase  of  fertility  in  the  successive  generations 
of  artificially  fertilized  hybrids,  in  contrast  with  those  spon¬ 
taneously  self-fertilized,  may,  as  I  believe,  be  accounted 
for  by  too  close  interbreeding  having  been  avoided. 


DEGREES  OF  STERILITY. 


281 


Now  let  us  turn  to  the  results  arrived  at  by  a  third  most 
experienced  hybridizer,  namely,  the  Hon.  and  Rev.  W. 
Herbert.  He  is  as  emphatic  in  his  conclusion  that  some 
hybrids  are  perfectly  fertile — as  fertile  as  the  pure  parent- 
species — as  are  Kolreuter  and  Gartner  that  some  degree  of 
sterility  between  distinct  species  is  a  universal  law  of 
nature.  He  experimented  on  some  of  the  very  same  species 
as  did  Gartner.  The  difference  in  their  results  may,  I 
think,  be  in  part  accounted  for  by  Herbert's  great  horticul¬ 
tural  skill,  and  by  his  having  hot-houses  at  his  command. 
Of  his  many  important  statements  I  will  here  give  only  a 
single  one  as  an  example,  namely,  that  “  every  ovule  in  a 
pod  of  Crinum  capense  fertilized  by  C.  revolutum  pro¬ 
duced  a  plant,  which  I  never  saw  to  occur  in  a  case  of  its 
natural  fecundation."  So  that  here  we  have  perfect,  or 
even  more  than  commonly  perfect  fertility,  in  a  first  cross 
between  two  distinct  species. 

This  case  of  the  Crinum  leads  me  to  refer  to  a  singular 
fact,  namely,  that  individual  plants  of  certain  species 
of  Lobelia,  Yerbascum  and  Passiflora,  can  easily  be  fer¬ 
tilized  by  the  pollen  from  a  distinct  species,  but  not  by 
pollen  from  the  same  plant,  though  this  pollen  can  be 
proved  to  be  perfectly  sound  by  fertilizing  other  plants  or 
species.  In  the  genus  Hippeastrum,  in  Corydalis  as 
shown  by  Professor  Hildebrand,  in  various  orchids  as 
shown  by  Mr.  Scott  and  Fritz  Muller,  all  the  individuals 
are  in  this  peculiar  condition.  So  that  with  some  species, 
certain  abnormal  individuals,  and  in  other  species  all  the 
individuals,  can  actually  be  hybridized  much  more  readily 
than  they  can  be  fertilized  by  pollen  from  the  same  indi¬ 
vidual  plant!  To  give  one  instance,  a  bulb  of  Hippeas¬ 
trum  aulicum  produced  four  flowers;  three  were  fertilized 
by  Herbert  with  their  own  pollen,  and  the  fourth  was  sub¬ 
sequently  fertilized  by  the  pollen  of  a  compound  hybrid 
descended  from  three  distinct  species:  the  result  was  that 
“the  ovaries  of  the  three  first  flowers  soon  ceased  to  grow, 
aud  after  a  few  days  perished  entirely,  whereas  the  pod 
impregnated  by  the  pollen  of  the  hybrid  made  vigorous 
growth  and  rapid  progress  to  maturity,  and  bore  good  seed, 
which  vegetated  freely."  Mr.  Herbert  tided  similar  experi¬ 
ments  during  many  years,  and  always  with  the  same  result. 
These  cases  serve  to  show  on  what  slight  and  mysterious 


282 


HYBRIDISM, ; 


causes  the  lesser  or  greater  fertility  of  a  species  sometimes 
depends. 

The  practical  experiments  of  horticulturists,  though  not 
made  with  scientific  precision,  deserve  some  notice.  It  is 
notorious  in  how  complicated  a  manner  the  species  of 
Pelargonium,  Fuchsia,  Calceolaria,  Petunia,  Rhododen¬ 
dron,  etc.,  have  been  crossed,  yet  many  of  these  hybrids 
seed  freely.  For  instance,  Herbert  asserts  that  a  hybrid 
from  Calceolaria  integrifolia  and  plantaginea,  species  most 
widely  dissimilar  in  general  habit,  “  reproduces  itself  as 
perfectly  as  if  it  had  been  a  natural  species  from  the 
mountains  of  Chili. ”  I  have  taken  some  pains  to  ascer¬ 
tain  the  degree  of  fertility  of  some-  of  the  complex  crosses 
of  Rhododendrons,  and  I  am  assured  that  many  of  them 
are  perfectly  fertile.  Mr.  C.  Noble,  for  instance,  informs 
me  that  he  raises  stocks  for  grafting  from  a  hybrid  between 
Rhod.  ponticum  and  catawbiense,  and  that  this  hybrid 
“  seeds  as  freely  as  it  is  possible  to  imagine.”  Had  hybrids, 
when  fairly  treated,  always  gone  on  decreasing  in  fertility 
in  each  successive  generation,  as  G&rtner  believed  to  be 
the  case,  the  fact  would  have  been  notorious  to  nursery¬ 
men.  Horticulturists  raise  large  beds  of  the  same  hybrid, 
and  such  alone  are  fairly  treated,  for  by  insect  agency  the 
several  individuals  are  allowed  to  cross  freely  with  each 
other,  and  the  injurious  influence  of  close  interbreeding  is 
thus  prevented.  Any  one  may  readily  convince  himself 
of  the  efficiency  of  insect  agency  by  examining  the  flowers 
of  the  more  sterile  kinds  of  hybrid  Rhododendrons,  which 
produce  no  pollen,  for  he  will  find  on  their  stigmas  plenty 
of  pollen  brought  from  other  flowers. 

In  regard  to  animals,  much  fewer  experiments  have  been 
carefully  tried  than  with  plants.  If  our  systematic  arrange¬ 
ments  can  be  trusted,  that  is,  if  the  genera  of  animals  are 
as  distinct  from  each  others  as  are  the  genera  of  plants, 
then  we  may  infer  that  animals  more  widely  distinct  in 
the  scale  of  nature  can  be  crossed  more  easily  than  in 
the  case  of  plants;  but  the  hybrids  themselves  are,  I 
think,  more  sterile.  It  should,  however,  be  borne  in 
mind  that,  owing  to  few  animals  breeding  freely 
under  confinement,  few  experiments  have  been  fairly 
tried:  for  instance,  the  canary-bird  has  been  crossed  with 
nine  distinct  species  of  finches,  but,  as  not  one  of  these 


DEGREES  OF  STERILITY.  283 

breeds  freely  in  confinement,  we  have  no  right  to  expect 
that  the  first  crosses  between  them  and  the  canary,  or  that 
their  hybrids,  should  be  perfectly  fertile.  Again,  with 
respect  to  the  fertility  in  successive  generations  of  the  more 
feitile  hybiid  animals,  I  hardly  know  of  an  instance  in 
which  two  families  of  the  same  hybrid  have  been  raised  at 
the  same  time  from  different  parents,  so  as  to  avoid  the  ill 
effects  of  close  interbreeding.  On  the  contrary,  brothers 
and  sisters  have  usually  been  crossed  in  each  successive 
generation,  in  opposition  to  the  constantly  repeated  admon¬ 
ition  of  every  breeder.  And  in  this  case,  it  is  not  at  all 
surprising  that  the  inherent  sterility  in  the  hybrids  should 
have  gone  on  increasing. 

Although  I  know  of  hardly  any  thoroughly  well-authen¬ 
ticated  cases  of  perfectly  fertile  hybrid  animals,  I  have 
leason  to  believe  that  the  hybrids  from  Cervulus  vaginalis 
and  Reevesii,  and  from  Phasianus  colchicus  with  P.  tor- 
quatus,  are  perfectly  fertile.  M.  Quatrefages  states  that 
the  hybrids  from  two  moths  (Bombyx  cynthia  and  arrindia) 
were  proved  in  Paris  to  be  fertile  inter  se  for  eight  genera¬ 
tions.  It  has  lately  been  asserted  that  two  such  distinct 
species  as  the  hare  and  rabbit,  when  they  can  be  got  to 
breed  together,  produce  offspring,  which  are  highly  fertile 
when  crossed  with  one  of  the  parent-species.  The  hybrids 
from  the  common  and  Chinese  geese  (A.  cygnoides),  species 
which  are  so  different  that  they  are  generally  ranked  in 
distinct  genera,  have  often  bred  in  this  country  with  either 
Pme  paieut,  and  in  one  single  instance  they  have  bred 
inter  se.  This  was  effected  by  Mr.  Eyton,  who  raised  two 
hybrids  from  the  same  parents,  but  from  different  hatches; 
and  from  these  two  birds  he  raised  no  less  than  eight 
hybiids  (grandchildren  of  the  pure  geese)  from  one  nest. 
In  India,  however,  these  cross-bred  geese  must  be  far  more 

i  ^  ic  TA1  .  by  two  eminently  capable  judges, 

namely  Mr.  Blyth  and  Captain  Ilutton,  that  whole  flocks 
ot  these  crossed  geese  are  kept  in  various  parts  of  the  coun¬ 
ty  ,  and  as.  they  are  kejit  for  profit,  where  neither  pure 
pai ent-species  exists,  they  must  certainly  be  highly  or  per¬ 
fectly  fertile.  -  1 

With  our  domesticated  animals,  the  various  races  when 
crossed  together  are  quite  fertile;  yet  in  many  cases  they 
aie  descended  from  two  or  more  wild  species.  From  this 


284 


LAWS  GOVERNING  THE  STERILITY 


fact  we  must  conclude  either  that  the  aboriginal  parent- 
species  at  first  produced  perfectly  fertile  hybnds,  or  t  a 
the  hybrids  subsequently  reared  under  domestication 
became  quite  fertile.  This  latter  alternative,  which  was 
first  propounded  by  Pallas,  seems  by  far  the  most  probable, 
and  can,  indeed,  hardly  be  doubted.  It  is,  for  instance, 
almost  certain  that  our  dogs  are  descended  from  several 
wild  stocks;  yet,  with  perhaps  the  exception  of  certain  in¬ 
digenous  domestic  dogs  of  South  America,  all  are  quite 
fertile  together;  but  analogy  makes  me  greatly  doubt, 
whether  the  several  aboriginal  species  would  at  first  have 
freely  bred  together  and  have  produced  quite  fertile  hybrids. 
So  again  I  have  lately  acquired  decisive  evidence  that  the 
crossed  offspring  from  the  Indian  humped  and  common 
cattle  are  inter  se  perfectly  fertile;  and  from  the  observa¬ 
tions  by  Rutimeyer  on  their  important  osteological  diffei- 
ences,  as  well  as  from  those  by  Mr.  Blyth  on  their  differences 
in  habits,  voice,  constitution,  etc.,  these  two  forms  must 
be  regarded  as  good  and  distinct  species.  The  same  remarks 
may  be  extended  to  the  two  chief  races  of  the  pig.  We 
must,  therefore,  either  give  up  the  belief  of  the  universal 
sterility  of  species  when  crossed;  or  we  must  look  at  this 
sterility  in  animals,  not  as  an  indelible  characteristic,  but 
as  one  capable  of  being  removed  by  domestication.  _ 
Finally,  considering  all  the  ascertained  facts  on  the  inter¬ 
crossing  of  plants  and  animals,  it  may  be  concluded  that 
some  degree  of  sterility,  both  in  first  crosses  and  in  hybrids, 
is  an  extremely  general  result;  but  that  it  cannot,  under 
our  present  state  of  knowledge,  be  considered  as  absolutely 

universal. 


LAWS  GOVERNING  THE  STERILITY  OF  FIRST  CROSSES  AND 

OF  HYBRIDS. 

We  will  now  consider  a  little  more  in  detail .  the  laws 
governing  the  sterility  of  first  crosses  and  of  hybnds.  ur 
chief  obiect  will  be  to"  see  whether  or  not  these  laws  indicate 
that  species  have  been  specially  endowed  with  this  quality, 
in  order  to  prevent  their  crossing  and  blending  together  m 
utter  confusion.  The  following  conclusions  are  drawn  up 
chiefly  from  Gartner’s  admirable  work  on  the  hybridization 
of  plants.  I  have  taken  much  pains  to  ascertain  how  far 
they  apply  to  animals,  and,  considering  how  scanty  our 


285 


OF  FIRST  CROSSES  AND  OF  HYBRIDS. 

knowledge  is  in  regard  to  hybrid  animals,  I  have  been  sur 
prised  to  find  how  generally  the  same  rules  apply  to  both 
kingdoms. 

It  has  been  already  remarked,  that  the  degree  of  fertility, 
both  of  first  crosses  and  of  hybrids,  graduates  from  zero  to 
perfect  fertility.  It  is  surprising  in  how  many  curious 
ways  this  gradation  can  be  shown;  but  only  the  barest 
outline  of  the  facts  can  here  be  given.  When  pollen  from 
a  plant  of  one  family  is  placed  on  the  stigma  of  a  plant  of 
a  distinct  family,  it  exerts  no  more  influence  than  so  much 
inorganic  dust.  From  this  absolute  zero  of  fertility,  the 
pollen  of  different  species  applied  to  the  stigma  of  some 
one  species  of  the  same  genus,  yields  a  perfect  gradation 
in  the  number  of  seeds  produced,  up  to  nearly  complete  or 
even  quite  complete  fertility;  and,  as  we  have  seen,  in  cer¬ 
tain  abnormal  cases,  even  to  an  excess  of  fertility,  beyond 
that  which  the  plant’s  own  pollen  produces.  So  in 
hybrids  themselves,  there  are  some  which  never  have  pro¬ 
duced,  and  probably  never  would  produce,  even  with  the 
pollen  of  the  pure  parents,  a  single  fertile  seed:  but  in 
some  of  these  cases  a  first  trace  of  fertility  may  be  detected, 
by  the  pollen  of  one  of  the  pare  parent-species  causing  the 
flower  of  the  hybrid  to  wither  earlier  than  it  otherwise 
would  have  done;  and  the  early  withering  of  the  flower  is 
well  known  to  be  a  sign  of  incipient  fertilization.  From 
this  extreme  degree  of  sterility  we  have  self-fertilized 
hybrids  producing  a  greater  and  greater  number  of  seeds 
up  to  perfect  fertility. 

The  hybrids  raised  from  two  species  which  are  very  diffi¬ 
cult  to  cross,  and  which  rarely  produce  any  offspring,  are 
generally  very  sterile;  but  the  parallelism  between  the 
difficulty  of  making  a  first  cross,  and  the  sterility  of  the 
hybrids  thus  produced— two  classes  of  facts  which  are 
generally  confounded  together— is  by  no  means  strict. 
There  are  many  cases,  in  which  two  pure  species,  as  in  the 
genus  Verbascum,  can  be  united  with  unusual  facility,  and 
produce  numerous  hybrid  offspring,  yet  these  hybrids  are 
remarkably  sterile.  On  the  other  hand,  there  are  species 
which  can  be  crossed  very  rarely,  or  with  extreme  difficulty, 
but  the  hybrids,  when  at  last  produced,  are  very  fertile. 
Even  within  the  limits  of  the  same  genus,  for  instance  in 
Dianthus,  these  two  opposite  cases  occur. 


286 


LAWS  GOVERNING  THE  STERILITY 


The  fertility,  both  of  first  crosses  and  of  hybrids,  is  more 
easilv  affected  by  unfavorable  conditions,  than  is  that  of 
pure" species.  But  the  fertility  of  first  crosses  is  likewise 
innately  variable;  for  it  is  not  always  the  same  in  degree 
when  the  same  two  species  are  crossed  under  the  same  cir¬ 
cumstances;  it  depends  in  part  upon  the  constitution  of 
the  individuals  which  happen  to  have  been  chosen  for  the 
experiment.  So  it  is  with  hybrids,  for  their  degree  of  fer¬ 
tility  is  often  found  to  differ  greatly  in  the  several  indi¬ 
viduals  raised  from  seed  out  of  the  same  capsule  and  ex¬ 
posed  to  the  same  conditions. 

By  the  term  systematic  affinity  is  meant,  the  general  re¬ 
semblance  between  species  in  structure  and  constitution. 
Now  the  fertility  of  first  crosses,  and  of  the  hybrids  pro¬ 
duced  from  them,  if  largely  governed  by  their  systematic 
affinity.  This  is  clearly  shown  by  hybrids  never  having 
been  raised  between  species  ranked  by  systematists  in  dis¬ 
tinct  families;  and  on  the  other  hand,  by  very  closely 
allied  species  generally  uniting  with  facility.  But  the  cor¬ 
respondence  between  systematic  affinity  and  the  facility  of 
crossing  is  by  no  means  strict.  A  multitude  of  cases  could 
be  given  of  very  closely  allied  species  which  will  not  unite, 
or  only  with  extreme  difficulty;  and  on  the  other  hand  of 
very  distinct  species  which  unite  with  the  utmost  facility. 
In  the  same  family  there  may  be  a  genus,  as  Dianthus,  in 
which  very  many  species  can  most  readily  be  crossed;  and 
another  genus,  as  Silene,  in  which  the  most  persevering 
efforts  have  failed  to  produce  between  extremely  close 
species  a  single  hybrid.  Even  within  the  limits  of  the 
same  genus,  "we  meet  with  this  same  difference;  for  in¬ 
stance,  the  many  species  of  Nicotiana  have  been  more 
largely  crossed  than  the  species  of  almost  any  other  genus; 
but  Gartner  found  that  N.  acuminata,  which  is  not  a  par¬ 
ticularly  distinct  species,  obstinately  failed  to  fertilize,  or 
to  be  fertilized,  by  no  less  than  eight  other  species  of  Nico¬ 
tiana.  Many  analogous  facts  could  be  given. 

No  one  has  been  able  to  point  out  what  kind  or  what 
amount  of  difference,  in  any  recognizable  character,  is  suf¬ 
ficient  to  prevent  two  species  crossing.  _  It  can  be  shown 
that  plants  most  widely  different  in  habit  and  general  ap¬ 
pearance,  and  having  strongly  marked  differences  in  every 
part  of  the  flower,  even  in  the  pollen,  in  the  fruit,  and  in 


OF  FIRST  CROSSES  AND  OF  HYBRIDS .  28? 

the  cotyledons,  can  be  crossed.  Annual  and  perennial 
plants,  deciduous  and  evergreen  trees,  plants  inhabiting 
different  stations  and  fitted  for  extremely  different  climates, 
can  often  be  crossed  with  ease. 

By  a  reciprocal  cross  between  two  species,  I  mean  the 
case,  for  instance,  of  a  female  ass  being  first  crossed  by  a 
stallion,  and  then  a  mare  by  a  male  ass;  these  cwo  species 
may  then  be  said  to  have  been  reciprocally  crossed. 
I  here  is  often  .  the  widest  possible  difference  in  the 
facility  of  making  reciprocal  crosses.  Such  cases  are 
highly  important,  for  they  prove  that  the  capacity  in 
any  two  species  to  cross  is  often  completely  independent 
of  their  sytematic  affinity,  that  is  of  any  difference 
in  their  structure  or  constitution,  excepting  in  their 
reproductive  systems.  The  diversity  of  the  result  in  recip¬ 
rocal  crosses  between  the  same  two  species  was  long  ago 
observed  by  Kolreuter.  To  give  an  instance:  Mirabilis 
jalapa  can  easily  be.  fertilized  by  the  pollen  of  M.  long- 
iflora,  and  the  hybrids  thus  produced  are  sufficiently  fer¬ 
tile;  but  Kolreuter  tried  more  than  two  hundred  times, 
during  eight  folio  wing  years,  to  fertilize  reciprocally  M.  long- 
iflora  with  the  pollen  of  M.  jalapa,  and  utterly  failed. 
Several  other  equally  striking  cases  could  begiven."  Thuret 
has  observed  the  same  fact  with  certain  sea-weeds  or  Fuci. 
Gartner,  moreover,  found  that  this  difference  of  facility  in 
making  reciprocal  crosses  is  extremely  common  in  a  lesser 
degree.  He  has  observed  it  even  between  closely  related 
forms  (as  IVfatthiola  annua  and  glabra)  which  many 
botanists  rank  only  as  varieties.  It  is  also  a  remarkable 
fact  that  hybrids  raised  from  reciprocal  crosses,  though  of 
course  compounded  of  the  very  same  two  species,  the  one 
species  having  first  been  used  as  the  father  and  then  as  the 
mother,  though  they  rarely  differ  in  external  characters, 
yet  generally  differ  in  fertility  in  a  small,  and  occasionally 
in  a  high  degree. 

Several  other  singular  rules  could  be  given  from  Gart- 
nei :  for  instance,  some  species  have  a  remarkable  power  of 
crossing  with  other  species;  other  species  of  the  same 
genus  have  a  remarkable  power  of  impressing  their  like¬ 
ness  on  their  hybrid  offspring;  but  these  two  powers  do  not 
at  all  necessarily  go  together.  There  are  certain  hybrids 
which,  instead  of  having,  as  is  usual,  an  intermediate 


288 


LAWS  GOVERNING  THE  STERILITY 


character  between  their  two  parents,  always  closely  resem¬ 
ble  one  of  them;  and  such  hybrids,  though  externally  so 
like  one  of  their  pure  parent-species,  are  with  rare  excep¬ 
tions  extremely  sterile.  So  again  among  hybrids  which 
are  usually  intermediate  in  structure  between  their  parents, 
exceptional  and  abnormal  individuals  sometimes  are  born, 
which  closely  resemble  one  of  their  pure  parents;  and  these 
hybrids  are  almost  always  utterly  sterile,  even  when  the 
other  hybrids  raised  from  seed  from  the  same  capsule  have 
a  considerable  degree  of  fertility*  These  facts  show  how 
completely  the  fertility  of  a  hybrid  may  be  independent  of 
its  external  resemblance  to  either  pure  parent. 

Considering  the  several  rules  now  given,  which  govern 
the  fertility  of  first  crosses  and  of  hybrids,  we  see  that 
when  forms,  which  must  be  considered  as  good  and  distinct 
species,  are  united,  their  fertility  graduates  from  zero  to 
perfect  fertility,  or  even  to  fertility  under  certain  con¬ 
ditions  in  excess;  that  their  fertility,  besides  being  emi¬ 
nently  susceptible  to  favorable  and  unfavorable  conditions, 
is  innately  variable;  that  it  is  by  no  means  always  the  same 
in  degree  in  the  first  cross  and  in  the  hybrids  produced 
from  this  cross;  that  the  fertility  of  hybrids  is  not  related 
to  the  degree  in  which  they  resemble  in  external  appearance 
either  parent;  and  lastly,  that  the  facility  of  making  a  first 
cross  between  any  two  species  is  not  always  governed  by 
their  systematic  affinity  or  degree  of  resemblance  to  each 
other.  This  latter  statement  is  clearly  proved  by  the  dif¬ 
ference  in  the  result  of  reciprocal  crosses  between  the  same 
two  species,  for,  according  as  the  one  species  or  the  other 
is  used  as  the  father  or  the  mother,  there  is  generally  some 
difference,  and  occasionally  the  widest  possible  dif¬ 
ference,  in  the  facility  of  effecting  an  union.  The 
hybrids,  moreover,  produced  from  reciprocal  crosses  often 
differ  in  fertility. 

Now,  do  these  complex  and  singular  rules  indicate 
that  species  have  been  endowed  with  sterility  simply  to 
prevent  their  becoming  confounded  in  nature?  I  think 
not.  For  why  should  the  sterility  be  so  extremely  differ¬ 
ent  in  degree,  when  various  species  are  crossed,  all  of  which 
we  must  suppose  it  would  be  equally  important  to  keep 
from  blending  together?  Why  should  the  degree  of 
sterility  be  innately  variable  in  the  individuals  of  the  same 


OF  FIRST  CROSSES  AND  OF  HYBRIDS. 


289 


species?  Why  should  some  species  cross  with  facility  and 
yet  produce  very  sterile  hybrids;  and  other  species  cross 
with  extreme  difficulty,  and  yet  produce  fairly  fertile 
hybrids?  Why  should  there  often  be  so  great  a  differ¬ 
ence  in  the  result  of  a  reciprocal  cross  between  the  same 
two  species?  Why,  it  may  even  be  asked,  has  the  pro¬ 
duction  of  hybrids  been  permitted  ?  To  grant  to  species 
the  special  power  of  producing  hybrids,  and  then  to  stop 
their  further  propagation  by  different  degrees  of  sterility, 
not  strictly  related  to  the  facility  of  the  first  union  between 
their  parents,  seems  a  strange  arrangement. 

The  foregoing  rules  and  facts,  on  the  other  hand,  appear 
to  me  clearly  to  indicate  that  the  sterility,  both  of  first 
crosses  and  of  hybrids,  is  simply  incidental  or  dependent  on 
unknown  differences  in  their  reproductive  systems;  the 
differences  being  of  so  peculiar  and  limited  a  nature,  that, 
in  reciprocal  crosses  between  the  same  two  species,  the 
male  sexual  element  of  the  one  will  often  freely  act  on  the 
female  sexual  element  of  the  other,  but  not  in  a  reversed 
direction.  It  will  be  advisable  to  explain  a  little  more 
fully,  by  an  example,  what  I  mean  by  sterility  being  inci¬ 
dental  on  other  differences,  and  not  a  specially  endowed 
quality.  As  the  capacity  of  one  plant  to  be  grafted  or 
budded  on  another  is  unimportant  for  their  welfare  in  a 
state  of  nature,  I  presume  that  no  one  will  suppose  that 
this  capacity  is  a  specially  endowed  quality,  but  will  admit 
that  it  is  incidental  on  differences  in  the  laws  of  growth  of 
the  two  plants.  We  can  sometimes  see  the  reason  why  one 
tree  will  not  take  on  another  from  differences  in  their  rate  of 
growth,  in  the  hardness  of  their  wood,  in  the  period  of  the 
flow  or  nature  of  their  sap,  etc. ;  but  in  a  multitude  of 
cases  we  can  assign  no  reason  whatever.  Great  diversity 
in  the  size  of  two  plants,  one  being  woody  and  the  other 
herbaceous,  one  being  evergreen  and  the  other  deciduous, 
and  adaptation  to  widely  different  climates,  do  not  always 
prevent  the  two  grafting  together.  As  in  hybridization,  so 
with  grafting,  the  capacity  is  limited  by  systematic  affinity, 
for  no  one  has  been  able  to  graft  together  trees  belonging 
to  quite  distinct  families;  and,  on  the  other  hand,  closely 
allied  species  and  varieties  of  the  same  species,  can  usually, 
but  not  invariably,  be  grafted  with  ease.  But  this  capacity, 
as  in  hybridization,  is  by  no  means  absolutely  governed  by 


2  9.0  LAWS  GO  VERNING  THE  ST  ERIE  1TY 

systematic  affinity.  Although  many  distinct  genera  within 
the  same  family  have  been  grafted  together,  in  other  cases 
species  of  the  same  genus  will  not  take  on  each  other.  I  lie 
pear  can  be  grafted  far  more  readily  on  the  quince,  which 
is  ranked  as  a  distinct  genus,  than  on  the  apple,  which  is  a 
member  of  the  same  genus.  Even  different  varieties  ot 
the  pear  take  with  different  degrees  of  facility  on  the 
quince;  so  do  different  varieties  of  the  apricot  and  peach 

on  certain  varieties  of  the  plum.  .  . 

As  Gartner  found  that  there  was  sometimes  an  innate 
difference  in  different  individuals  of  the  same  two 
species  in  crossing;  so  Sageret  believes  this  to  be  the 
case  with  different  individuals  of  the  same  two  species 
in  being  grafted  together.  As  in  reciprocal  crosses,  the 
facility  of  effecting  an  union  is  often  very  far  from  equal, 
so  it  sometimes  is  in  grafting.  The  common  goosebeny, 
for  instance,  cannot  be  grafted  on  the  currant,  whereas 
the  currant  will  take,  though  with  difficulty,  on  the 

&°  We  have  seen  that  the  sterility  of  hybrids  which  have 
their  reproductive  organs  in  an  imperfect  condition,  is  a 
different  case  from  the  difficulty  of  uniting  two  pure  spe¬ 
cies  which  have  their  reproductive  organs  perfect;  yet 
these  two  distinct  classes  of  cases  run  to  a  large  extent 
parallel.  Something  analogous  occurs  m  grafting;  tor 
Thouin  found  that  three  species  of  Robima,  which  seeded 
freely  on  their  own  roots,  and  which  could  be  grafted  with 
no  great  difficulty  on  a  fourth  species,  when  thus  grafted 
were  rendered  barren.  On  the  other  hand,  certain  species 
of  Sorbus,  when  grafted  on  other  species,  yielded  twice 
as  much  fruit  as  when  on  their  own  roots.  We  are  re¬ 
minded  by  this  latter  fact  of  the  extraordinary  cases  oi 
hippeastrum,  passiflora,  etc.,  which  seed  much  moie  fiee  y 
when  fertilized  with  the  pollen  of  a  distinct  species  than 
when  fertilized  with  pollen  from  the  same  plant. 

We  thus  see  that,  although  there  is  a  clear  and  gieat  dr  - 
ference  between  the  mere  adhesion  of  grafted  stocks  an 
the  union  of  the  male  and  female  elements  in  the  act  ot 
reproduction,  yet  that  there  is  a  rude  degree  of  parallelism 
in  the  results  of  grafting  and  of  crossing  distinct  species. 
And  as  we  must  look  at  the  curious  and  complex  laws  &ov* 
erning  the  facility  with  which  trees  can  be  grafted  on  each 


291 


OF  FIRST  CROSSES  AND  OF  HYBRIDS. 

other  as  incidental  on  unknown  differences  in  their  vege¬ 
tative  systems,  so  I  believe  that  the  still  more  complex 
laws  governing  the  facility  of  first  crosses  are  incidental  on 
unknown  differences  in  their  reproductive  systems.  These 
diffeiences  in  both  cases  follow,  to  a  certain  extent,  as 
might  have  been  expected,  systematic  affinity,  by  which 
term  every  kind  of  resemblance  and  dissimilarity  between 
organic  beings  is  attempted  to  be  expressed.  The  facts  by 
no  means  seem  to  indicate  that  the  greater  or  lesser  diffi¬ 
culty  of  either  grafting  or  crossing  various  species  has  been 
a  special  endowment;  although  in  the  case  of  crossing,  the 
difficulty  is  as  important  for  the  endurance  and  stability  of 
specific  forms  as  in  the  case  of  grafting  it  is  unimportant 
for  their  welfare. 

origin  and  causes  of  the  sterility  of  first  crosses 

AND  OF  HYBRIDS. 

At  one  time  it  appeared  to  me  probable,  as  it  has  to  others, 
that  the  sterility  of  first  crosses  and  of  hybrids  might  have 
been  slowly  acquired  through  the  natural  selection  of 
slightly  lessened  degrees  of  fertility,  which,  like  any  other 
variation,  spontaneously  appeared  in  certain  individuals  of 
one  variety  when  crossed  with  those  of  another  variety. 
For  it  would  clearly  be  advantageous  to  two  varieties  or 
incipient  species  if  they  could  be  kept  from  blending,  on 
the  same  principle  that,  when  man  is  selecting  at  the 
same  time  two  varieties,  it  is  necessary  that  he  should 
keep  them  separate.  In  the  first  place,  it  may  be  re¬ 
marked  that  species  inhabiting  distinct  regions  are  often 
sterile  when  crossed;  now  it  could  clearly  have  been  of 
no  advantage  to  such  separated  species  to  have  been 
rendered  mutually  sterile,  and  consequently  this  could 
not  have  been  effected  through  natural  selection;  but 
it  may  perhaps  be  argued,  that,  if  a  species  was  rendered 
sterile  with  some  one  compatriot,  sterility  with  other  spe¬ 
cies  would  follow  as  a  necessary  contingencv.  In  the 
second  place,  it  is  almost  as  much  opposed  to  the  theory  of 
natural  selection  as  to  that  of  special  creation,  that  in  re- 
cipiocal  ciosses  the  male  element  of  one  form  should  have 
been  rendered  utterly  impotent  on  a  second  form,  while  at 
the  same  time  the  male  element  of  khis  second  form  is  en- 


292  CA  USES  OF  THE  STERILITY 

abled  freely  to  fertilize  the  first  form;  for  this  peculiar 
state  of  the  reproductive  system  could  hardly  have  been 

advantageous  to  either  species.  _  .  , 

In  considering  the  probability  of  natural  selection  having 
come  into  action,  in  rendering  species  mutually  sterile,  the 
greatest  difficulty  will  be  found  to  lie  in  the  existence  of 
many  graduated  steps,  from  slightly  lessened  fertility  to  ab¬ 
solute  sterility.  It  may  he  admitted  that  it  would  profit  an 
incipient  species,  if  it  were  rendered  in  some  slight  degiee 
sterile  when  crossed  with  its  parent  form  or  with  some 
other  variety;  for  thus  fewer  bastardized  and  deteriorated 
offspring  would  be  produced  to  commingle  their  blood  with 
the  new  species  in  process  of  formation.  But  he  who  will 
take  the  trouble  to  reflect  on  the  steps  by  which  this  first 
degree  of  sterility  could  be  increased  through  natural  selec¬ 
tion  to  that  high  degree  which  is  common  with  so  many 
species,  and  which  is  universal  with  species  which  have 
been  differentiated  to  a  generic  or  family  rank,  will  find 
the  subject  extraordinarily  complex.  After  mature  reflec¬ 
tion  it  seems  to  me  that  this  could  not  have  been  effected 
through  natural  selection.  Take  the  case  of  any  two  spe¬ 
cies  which,  when  crossed,  produced  few  and  sterile  off¬ 
spring;  now,  what  is  there  which  could  favor  the  survival 
of  those  individuals  which  happened  to  be  endowed  m  a 
slightly  higher  degree  with  mutual  infertility,  and  whic 
thus  approached  by  one  small  step  toward  absolute  sterility. 
Yet  an  advance  of  this  kind,  if  the  theory  of  natuial  se¬ 
lection  be  brought  to  bear,  must  have  incessantly  occurred 
with  many  species,  for  a  multitude  are  mutually  quite 
barren.  With  sterile  neuter  insects  we  have  reason  to  be¬ 
lieve  that  modifications  in  their  structure  and  fertility 
have  been  slowly  accumulated  by  natural  selection,  trom 
an  advantage  having  been  thus  indirectly  given  to  the  com¬ 
munity  to  which  they  belonged  over  other  communities  of 
the  same  species;  but  an  individual  animal  not  belonging 
to  a  social  community,  if  rendered  slightly  sterile  when 
crossed  with  some  other  variety,  would  not  thus  itself  gain 
any  advantage  or  indirectly  give  any  advantage  to  the  other 
individuals  of  the  same  variety,  thus  leading  to  their  pieser- 

vation.  ...  ,.  • 

But  it  would  be  superfluous  to  discuss  this  question  in 

detail:  for  with  plants  wa  have  conclusive  evidence  that 


OF  FIRST  CROSSES  AND  OF  HYBRIDS.  393 

the  sterility  of  crossed  species  must  be  due  to  some  princi- 
pie,  quite  independent  of  natural  selection.  Both  Gartner 
and  Kolreuter  have  proved  that  in  genera  including  numer¬ 
ous  species,  a  series  can  be  formed  from  species  which  when 
crossed  yield  fewer  and  fewer  seeds,  to  species  which  never 
produce  a  single  seed,  but  yet  are  affected  by  the  pollen  of 
certain  other  species,  for  the  germen  swells.  It  is  here 
manifestly  impossible  to  select  the  more  sterile  individuals 
which  have  already  ceased  to  yield  seeds;  so  that  this  acme 
ot  sterility,  when  the  germen  alone  is  effected,  cannot  have 
been  gained  through  selection;  and  from  the  laws  govern¬ 
ing  the  various  grades  of  sterility  being  so  uniform  through¬ 
out  the  animal  and  vegetable  kingdoms,  we  may  infer  that 
the  cause,  whatever  it  may  be,  is  the  same  or  nearly  the 
same  m  all  cases. 

We  will  now  look  a  little  closer  at  the  probable  nature 
of  the  differences  between  species  which  induce  sterility  in 
first  ciosses  and  in  hybrids.  In  the  case  of  first  crosses, 
the  greater  or  less  difficulty  in  effecting  an  union  and  in 
obtaining  offspring  apparently  depends  on  several  distinct 
causes.  There  must  sometimes  be  a  physical  impossibility 
m  the  male  element  reaching  the  ovule,  as  would  be  the 
case  with  a  plant  having  a  pistil  too  long  for  the  pollen- 
tubes  to  reach  the  ovarium.  It  has  also  been  observed  that 
when  the  pollen  of  one  species  is  placed  on  the  stigma  of  a 
allied  species,  though  the  pollen-tubes  protrude, 
they  do  not  penetrate  the  stigmatic  surface.  Again,  the 
male  element  may  reach  the  female  element,  but  be  inca¬ 
pable  of  causing  an  embryo  to  be  developed,  as  seems  to 
have  been  tbe  case  with  some  of  Thureffs  experiments  on 
uci.  -No  explanation  can  be  given  of  these  facts,  any 
more  than  why  certain  trees  can  not  be  grafted  on  others. 
Lastly,  an  embryo  may  be  developed,  and  then  perish  at 
an  early  period.  This  latter  alternative  has  not  been  suf¬ 
ficiently  attended  to;  but  I  believe,  from  observations  com¬ 
municated  to  me  by  Mr.  Hewitt,  who  has  had  great  ex¬ 
perience  m  hybridizing  pheasants  and  fowls,  that  the  early 
death  of  the  embryo  is  a  very  frequent  cause  of  sterility  in 
first  crosses. .  Mr.  Salter  has  recently  given  the  results  of 
an  examination  of  about  500  eggs  produced  from  various 
crosses  between  three  species  of  Gallus  and  their  hybrids: 


294 


CA  USES  OF  THE  STERILIT7 


the  majority  of  these  eggs  had  been  fertilized;  and  ia  the 
majority  of  the  fertilized  eggs,  the  embryos  had  either  been 
partially  developed  and  had  then  perished,  or  had  become 
nearly  mature,  but  the  young  chickens  had  been  unable 
to  break  through  the  shell.  Of  the  chickens  which  were 
born,  more  than  four-fifths  died  within  the  first  few  days, 
or  at  latest  weeks,  “  without  any  obvious  cause,  apparently 
from  mere  inability  to  live;”  so  that  from  the  500  eggs  only 
twelve  chickens  were  reared.  With  plants,  hybridized  em¬ 
bryos  probably  often  perish  in  a  like  manner;  at  least  it  is 
known  that  hybrids  raised  from  very  distinct  species  are 
sometimes  weak  and  dwarfed,  and  perish  at  an  early  age; 
of  which  fact  Max  Wichura  has  recently  given  some  strik¬ 
ing  cases  with  hybrid  willows.  It  may  be  here  worth 
noticing  that  in  some  cases  of  parthenogenesis,  the  em¬ 
bryos  within  the  eggs  of  silk  moths  which  had  not  been 
fertilized,  pass  through  their  early  stages  of  development 
and  then  perish  like  the  embryos  produced  by  a  cross  be¬ 
tween  distinct  species.  Until  becoming  acquainted  with 
these  facts,  I  was  unwilling  to  believe  in  the  frequent  early 
death  of  hybrid  embryos;  for  hybrids,  when  once  born,  are 
generally  healthy  and  long-lived,  as  we  see  in  the  case  of 
the  common  mule.  Hybrids,  however,  are  differently  cir¬ 
cumstanced  before  and  after  birth:  when  born  and  living 
in  a  country  where  their  two  parents  live,  they  are  gener¬ 
ally  placed  under  suitable  conditions  of  life.  But  a  hybrid 
partakes  of  only  half  of  the  nature  and  constitution  of  its 
mother;  it  may  therefore,  before  birth,  as  long  as  it  is 
nourished  within  its  mother’s  womb,  or  within  the  egg  or 
seed  produced  by  the  mother,  be  exposed  to  conditions  in 
some  degree  unsuitable,  and  consequently  be  liable  to 
perish  at  an  early  period;  more  especially  as  all  very  young 
beings  are  eminently  sensitive  to  injurious  or  unnatural 
conditions  of  life.  But  after  all,  the  cause  more  probably 
lies  in  some  imperfection  in  the  original  act  of  impregna¬ 
tion,  causing  the  embryo  to  be  imperfectly  developed, 
rather  than  in  the  conditions  to  which  it  is  subsequently 
exposed. 

In  regard  to  the  sterility  of  hybrids,  in  which  the  sexual 
elements  are  imperfectly  developed,  the  case  is  somewhat 
different.  I  have  more  than  once  alluded  to  a  large  body 
of  facts  showing  that,  when  animals  and  plants  are 


OF  FIRST  CROSSES  AND  OF  HYBRIDS.  295 

removed  from  their  natural  conditions,  they  are  extremely 
liable  to  have  their  reproductive  systems  seriously  affected. 
This,  in  fact,  is  the  great  bar  to  the  domestication  of  ani¬ 
mals.  Between  the  sterility  thus  superinduced  and  that  of 
hybrids,  there  are  many  points  of  similarity.  In  both 
cases  the  sterility  j.s  independent  of  general  health,  and  is 
often  accompanied  by  excess  of  size  or  great  luxuriance. 
In  both  cases  the  sterility  occurs  in  various  degrees;  in 
both,  the  male  element  is  the  most  liable  to  be  affected; 
but  sometimes  the  female  more  than  the  male.  In  both, 
the  tendency  goes  to  a  certain  extent  with  systematic  affi¬ 
nity,  for  whole  groups  of  animals  and  plants  are  rendered 
impotent  by  the  same  unnatural  conditions;  and  whole 
groups  of  species  tend  to  produce  sterile  hybrids.  On  the 
other  hand,  one  species  in  a  group  will  sometimes  resist 
great  changes  of  conditions  with  unimpaired  fertility;  and 
certain  species  in  a  group  will  produce  unusually  fertile 
hybrids.  No  one  can  tell  till  he  tries,  whether  any  partic¬ 
ular  animal  will  breed  under  confinement,  or  any  exotic 
plant  seed  freely  under  culture;  nor  can  he  tell  till  he 
tries,  whether  any  two  species  of  a  genus  will  produce  more 
or  less  sterile  hybrids.  Lastly,  when  organic  beings  are 
placed  during  several  generations  under  conditions  not 
natural  to  them,  they  are  extremely  liable  to  vary,  which 
seems  to  be  partly  due  to  their  reproductive  systems  having 
been  specially  affected,  though  in  a  lesser  degree  than  when 
sterility  ensues.  So  it  is  with  hybrids,  for  their  offspring 
in  successive  generations  are  eminently  liable  to  vary,  as 
every  experimentalist  has  observed. 

Thus  we  see  that  when  organic  beings  are  placed  under 
new  and  unnatural  conditions,  and  when  hybrids  are  pro¬ 
duced  by  the  unnatural  crossing  of  two  species,  the  repro¬ 
ductive  ^  system,  independently  of  the  general  state  of 
health,  is  affected  in  a  very  similar  manner.  In  the  one 
case,  the  conditions  of  life  have  been  disturbed,  though 
often  in  so  slight  a  degree  as  to  be  inappreciable  by  us;  in 
the  other  case,  or  that  of  hybrids,  the  external  conditions 
have  remained  the  same,  but  the  organization  has  been  dis¬ 
turbed  by  two  distinct  structures  and  constitutions,  includ¬ 
ing  of  course  the  reproductive  systems,  having  been 
blended  into  one.  For  it  is  scarcely  possible  that  two 
organizations  should  be  compounded  into  one,  without 


296 


CA  USES  OF  THE  STERILITY 


some  disturbance  occurring  in  the  development,  or  periodi¬ 
cal  action,  or  mutual  relations  of  the  different  parts  and 
organs  one  to  another  or  to  the  conditions  of  life.  When 
hybrids  are  able  to  breed  inter  se,  they  transmit  to  their 
offspring  from  generation  to  generation  the  same  com¬ 
pounded  organization,  and  hence  we  need  not  be  surprised 
that  their  sterility,  though  in  some  degree  variable,  does 
not  diminish;  it  is  even  apt  to  increase,  this  being  gener¬ 
ally  the  result,  as  before  explained,  of  too  close  interbreed¬ 
ing.  The  above  view  of  the  sterility  of  hybrids  being 
caused  by  two  constitutions  being  compounded  into  one 
has  been  strongly  maintained  by  Max  Wichura. 

It  must,  however,  be  owned  that  we  cannot  understand, 
on  the  above  or  any  other  view,  several  facts  with  respect 
to  the  sterility  of  hybrids;  for  instance,  the  unequal  fer¬ 
tility  of  hybrids  produced  from  reciprocal  crosses;  or  the 
increased  sterility  in  those  hybrids  which  occasionally  and 
exceptionally  resemble  closely  either  pure  parent.  Nor  do 
I  pretend  that  the  foregoing  remarks  go  to  the  root  of  the 
matter;  no  explanation  is  offered  why  an  organism,  when 
placed  under  unnatural  conditions,  is  rendered  sterile.  All 
that  I  have  attempted  to  show  is,  that  in  two  cases,  in 
some  respects  allied,  sterility  is  the  common  result — in  the 
one  case  from  the  conditions  of  life  having  been  disturbed, 
in  the  other  case  from  the  organization  having  been  dis¬ 
turbed  by  two  organizations  being  compounded  into  one. 

A  similar  parallelism  holds  good  with  an  allied  yet  very 
different  class  of  facts.  It  is  an  old  and  almost  universal 
belief,  founded  on  a  considerable  body  of  evidence,  which  I 
have  elsewhere  given,  that  slight  changes  in  the  conditions 
of  life  are  beneficial  to  all  living  things.  We  see  this  acted 
on  by  farmers  and  gardeners  in  their  frequent  exchanges 
of  seed,  tubers,  etc.,  from  one  soil  or  climate  to  another, 
and  back  again.  During  the  convalescence  of  animals, 
great  benefit  is  derived  from  almost  any  change  in  their 
habits  of  life.  Again,  both  with  plants  and  animals,  there 
is  the  clearest  evidence  that  a  cross  between  individuals  of 
the  same  species,  which  differ  to  a  certain  extent,  gives 
vigor  and  fertility  to  the  offspring;  and  that  close  inter¬ 
breeding  continued  during  several  generations  between  the 
nearest  relations,  if  these  be  kept  under  the  same  conditions 
of  life,  almost  always  leads  to  decreased  size,  weakness,  or 
sterility- 


OF  FIRST  CROSSES  AND  OF  H  YBR1DS.  a9? 

Hence  it  seems  that,  on  the  one  hand,  slight  changes  in 
the  conditions  of  life  benefit  all  organic  beings,  and  on  the 
othei  hand,  that  slight  crosses,  that  is,  crosses  between  the 
males  and  females  of  the  same  species,  which  have  been 
subjected  to  slightly  different  conditions,  or  which  have 
slightly  varied,  give  vigor  and  fertility  to  the  offspring 
-3,  ^s  we  have  seen,  organic  beings  long  habituated  to 
ceitam  uniform  conditions  under  a  state  of  nature,  when 
subjected,  as  under  confinement,  to  a  considerable  change 
in  their  conditions,  very  frequently  are  rendered  more  or 
less  sterile;  and  we  know  that  a  cross  between  two  forms 
that  have  become  widely  or  specifically  different,  produce 
hybrids  which  are  almost  always  in  some  degree  sterile  I 
am  fully  persuaded  that  this  double  parallelism  is  by  no 
means  an  accident  or  an  illusion.  He  who  is  able  to  ex¬ 
plain  why  the  elephant,  and  a  multidude  of  other  animals 
are  incapable  of  breeding  when  kept  under  only  partial 
confinement  m  their  native  country,  will  be  able  to  explain 
the  primary  cause  of  hybrids  being  so  generally  sterile, 
lie  will  at  the  same  time  be  able  to  explain  how  it  is  that 
the  races  of  some  of  our  domesticated  animals,  which  have 
often  been  subjected  to  new  and  net  uniform  conditions, 
are  quite  fertile  together,  although  they  are  descended  from 
distinct  species,  which  would  probably  have  been  sterile  if 
aboriginally  crossed.  The  above  two  parallel  series  of  facts 
seem  to  be  connected  together  by  some  common  but  un- 
known  bond,  which  is  essentially  related  to  the  principle 
of  life;  this  principle,  according  to  Mr.  Herbert  Spencer, 
being  that  life  depends  on,  or  consists  in,  the  incessant 
action  and  reaction  of  various  forces,  which,  as  throughout 
nature,  are  always  tending  toward  an  equilibrium;  and 
when  this  tendency  is  slightly  disturbed  by  any  change, 
the  vital  forces  gam  in  power.  *  ’ 

RECIPROCAL  DIMORPHISM  AKD  TRIMORPHISM. 

This  subject  may  be  here  briefly  discussed,  and  will  be 
found  to  throw  some  light  on  hybridism.  Several  plants 
belonging  to  distinct  orders  present  two  forms,  which 
exist  in  about  equal  numbers  and  which  differ  in  no  respect 
except  m  their  reproductive  organs;  one  form  having  a 
°ng  pistil  with  short  stamens,  the  other  a  short  pistil 


298 


reciprocal  dimorphism 


with  long  stamens;  the  two  having  differently  sized  pollen- 
grains.  With  trimorpliic  plants  there  are  three  forms 
likewise  differing  in  the  lengths  of  their  pistils  and  stamens, 
in  the  size  and  color  of  the  pollen-grains,  and  m  some 
other  respects;  and  as  in  each  of  the  three  forms  there  are 
two  sets  of  stamens,  the  three  forms  possess  altogethei  six 
sets  of  stamens  and  three  kinds  of  pistils.  These  organs 
are  so  proportioned  in  length  to  each  other  that  half  the 
stamens  in  two  of  the  forms  stand  on  a  level  with  the 
stigma  of  the  third  form.  Now  I  have  shown,  and  the 
result  has  been  confirmed  by  other  observers,  that  in 
order  to  obtain  full  fertility  with  these  plants,  it  is  neces- 
sary  that  the  stigma  of  the  one  form  should  be  fertilized 
by  pollen  taken  from  the  stamens  of  corresponding  height 
in  another  form.  So  that  with  dimorphic  species  two 
unions,  which  may  be  called  legitimate,  are  fully  lei  tile, 
and  two,  which  may  be  called  illegitimate,  are  more  or  less 
infertile.  With  trimorpliic  species  six  unions  are  legiti¬ 
mate.  or  fully  fertile,  and  twelve  are  illegitimate,  or  moie 

or  less  infertile.  ,  ..  .  . 

The  infertility  which  may  be  observed  m  various  dimor¬ 
phic  and  trimorpliic  plants,  when  they  are  illegitimately 
fertilized,  that  is  by  pollen  taken  from  stamens  not  cor¬ 
responding  in  height  with  the  pistil,  differs  much  m  degree, 
up  to  absolute  and  utter  sterility;  just  in  the  same  manner 
as  occurs  in  crossing  distinct  species.  As  the  degree  of 
sterility  in  the  latter  case  depends  in  an  eminent  degiee  on 
the  conditions  of  life  being  more  or  less  favorable,  so  I 
have  found  it  with  illegitimate  unions.  It  is  well  known 
that  if  pollen  of  a  distinct  species  be  placed  on  the  stigma 
of  a  flower,  and  its  own  pollen  be  afterward,  even  after 
a  considerable  interval  of  time,  placed  on  the  same  stigma, 
its  action  is  so  strongly  prepotent  that  it  generally  annihi¬ 
lates  the  effect  of  the  foreign  pollen;  so  it  is  with  the  pollen 
of  the  several  forms  of  the  same  species,  for  legitimate 
pollen  is  strongly  prepotent  over  illegitimate  pollen,  when 
both  are  placed  on  the  same  stigma.  I  ascertained  this 
by  fertilizing  several  flowers,  first  illegitimately,  and  twenty- 
four  hours  afterward  legitimately,  with  pollen  taken 
from  a  peculiarly  colored  variety,  and  all  the  seedling 
were  similarly  colored;  this  shows  that  the  legitimate  pollen, 
though  applied  twenty-four  hours  subsequently,  had 


AND  TRIMORPHISM. 


299 


wholly  destroyed  or  prevented  the  action  of  the  previously 
applied  illegitimate  pollen.  Again,  as  in  making  recipro¬ 
cal  crosses  between  the  same  two  species,  there  is  occa¬ 
sionally  a  great  difference  in  the  result,  so  the  same  thing 
occurs  with  trimorphic  plants;  for  instance,  the  mid- 
sty  led  form  of  Ly thrum  salicaria  was  illegitimately  fer¬ 
tilized  with  the  greatest  ease  by  pollen  from  the  longer 
stamens  of  the  short-styled  form,  and  yielded  many  seeds; 
but  the  latter  form  did  not  yield  a  single  seed  when  fer¬ 
tilized  by  the  longer  stamens  of  the  mid-styled  form. 

In  all  these  respects,  and  in  others  which  might  be 
added,  the  forms  of  the  same  undoubted  species,  when 
illegitimately  united,  behave  in  exactly  the  same  manner  as 
do  two  distinct  species  when  crossed.  This  led  me  carefully 
to  observe  during  four  years  many  seedlings,  raised  from 
several  illegitimate  unions.  The  chief  result  is  that  these 
illegitimate  plants,  as  they  may  be  called,  are  not 
fully  fertile.  It  is  possible  to  raise  from  dimorphic  species, 
both  long-styled  and  short-syled  illegitimate  plants,  and 
from  trimorphic  plants  all  three  illegitimate  forms.  These 
can  then  be  properly  united  in  a  legitimate  manner.  When 
this  is  done,  there  is  no  apparent  reason  why  they  should 
not  yield  as .  many  seeds  as  did  their  parents  when  legiti¬ 
mately  fertilized.  But  such  is  not  the  case.  They  are  all 
infertile,  in  various  degrees;  some  being  so  utterly  and  in¬ 
curably  sterile  that  they  did  not  yield  during  four  seasons 
a  single  seed  or  even  seed-capsule.  The  sterility  of  these 
illegitimate  plants,  when  united  with  each  other  in  a  legiti¬ 
mate  manner,  may  be  strictly  compared  with  that  of 
hybrids  when  crossed  inter  se.  If,  on  the  other  hand,  a 
hybrid  is  crossed  with  either  pure  parent-species,  the  ster¬ 
ility  is  usually  much  lessened:  and  so  it  is  when  an  illegiti¬ 
mate  plant  is  fertilized  by  a  legitimate  plant.  In  the 
same  manner  as  the  sterility  of  hybrids  does  not  always  run 
parallel  with  the  difficulty  of  making  the  first  cross  between 
the  two  parent-species,  so  that  sterility  of  certain  illegiti¬ 
mate  plants  was  unusually  great,  while  the  sterility  of  the 
union  from  which  they  were  derived  was  by  no  means 
great.  With  hybrids  raised  from  the  same  seed-capsule 
the  degree  of  sterility  is  innately  variable,  so  it  is  in  a 
marked  manner  with  illegitimate  plants.  Lastly,  many 
hybrids  are  profuse  and  persistent  flower ers,  while  other 


300 


RECIPROCAL  DIMORPHISM 


and  more  sterile  hybrids  produce  few  flowers,  and  are  weak, 
miserable  dwarfs;  exactly  similar  cases  occur  with  the 
illegitimate  offspring  of  various  dimorphic  and  trimorphie 
plants. 

Altogether  there  is  the  closest  indentity  in  character  and 
behavior  between  illegitimate  plants  and  hybrids.  It  is 
hardly  an  exaggeration  to  maintain  that  illegitimate  plants 
are  hybrids,  produced  within  the  limits  of  the  same  species 
by  the  improper  union  of  certain  forms,  while  ordinary 
hybrids  are  produced  from  an  improper  union  between  so- 
called  distinct  species.  We  have  also  already  seen  that 
there  is  the  closest  similarity  in  all  respects  between  first 
illegitimate  unions  and  first  crosses  between  distinct  species. 
This  will  perhaps  be  made  more  fully  apparent  by  an  illus¬ 
tration;  we  may  suppose  that  a  botanist  found  two  well- 
marked  varieties  (and  such  occur)  of  the  long-styled  form 
of  the  trimorphie  Lythrum  salicaria,  and  that  he  deter¬ 
mined  to  try  by  crossing  whether  they  were  specifically 
distinct.  He  would  find  that  they  yielded  only  about  one- 
fifth  of  the  proper  number  of  seed,  and  that  they  behaved 
in  all  the  other  above  specified  respects  as  if  they  had 
been  two  distinct  species.  But  to  make  the  case  sure,  he 
would  raise  plants  from  his  supposed  hybridized  seed,  and 
he  would  find  that  the  seedlings  were  miserably  dwarfed 
and  utterly  sterile,  and  that  they  behaved  in  all  other 
respects  like  ordinary  hybrids.  He  might  then  maintain 
that  he  had  actually  proved,  in  accordance  with  the  com¬ 
mon  view,  that  his  two  varieties  were  as  good  and  as  dis¬ 
tinct  species  as  any  in  the  world;  but  he  would  be  com¬ 
pletely  mistaken. 

The  facts  now  given  on  dimorphic  and  trimorphie  plants 
are  important,  because  they  show  us,  first,  that  the  physio¬ 
logical  test  of  lessened  fertility,  both  in  first  crosses  and  in 
hybrids,  is  no  safe  criterion  of  specific  distinction;  secondly, 
because  we  may  conclude  that  there  is  some  unknown  bond 
which  connects  the  infertility  of  illegitimate  unions  with 
that  of  their  illegitimate  offspring,  and  we  are  led  to 
extend  the  same  view  to  first  crosses  and  hybrids;  thirdly, 
because  we  find,  and  this  seems  -to  me  of  especial  impor¬ 
tance,  that  two  or  three  forms  of  the  same  species  may 
exist  and  may  differ  in  no  respect  whatever,  either  in 
structure  or  in  constitution,  relatively  to  external  con- 


AND  TRIMORPHISM. 


301 


ditions,  and  yet  be  sterile  when  united  in  certain  ways. 
For  we  must  remember  that  it  is  the  union  of  the  sexual 
elements  of  individuals  of  the  same  form,  for  instance,  of 
two  long-styled  forms,  which  results  in  sterility;  while  it 
is  the  union  of  the  sexual  elements  proper  to  two  distinct 
forms  which  is  fertile.  Hence  the  case  appears  at  first  sight 
exactly  the  reverse  of  what  occurs,  in  the  ordinary  unions 
of  the  individuals  of  the  same  species  and  with  crosses 
between  distinct  species.  It  is,  however,  doubtful  whether 
this  is  really  so;  but  I  will  not  enlarge  on  this  obscure 
subject. 

We  may,  however,  infer  as  probable  from  the  considera¬ 
tion  of  dimorphic  and  trimorphic  plants,  that  the  sterility 
of  distinct  species  when  crossed  and  of  their  hybrid  pro- 
geny,  depends  exclusively  on  the  nature  of  their  sexual 
elements,  and  not  on  any  difference  in  their  structure  or 
general  constitution.  We  are  also  led  to  this  same  con¬ 
clusion  by  considering  reciprocal  crosses,  in  which  the 
male  of  one  species  cannot  be  united,  or  can  be  united 
with  great  difficulty,  with  the  female  of  a  second  species, 
while  the  converse  cross  can  be  effected  with  perfect 
facility.  That  excellent  observer,  Gartner,  likewise  con¬ 
cluded  that  species  when  crossed  are  sterile  owing  to  dif¬ 
ferences  confined  to  their  reproductive  systems. 

FERTILITY  OF  VARIETIES  WHEN  CROSSED,  AND  OF  THEIR 
MONGREL  OFFSPRING,  NOT  UNIVERSAL. 

It  may  be  urged  as  an  overwhelming  argument  that 
there  must  be  some  essential  distinction  between  species 
and  varieties,  inasmuch  as  the  latter,  however  much  they 
may  differ  from  each  other  in  external  appearance,  cross 
with  perfect  facility,  and  yield  perfectly  fertile  offspring. 
With  some  exceptions,  presently  to  be  given,  I  fully  admit 
that  this  is  the  rule.  But  the  subject  is  surrounded  by 
difficulties,  for,  looking  to  varieties  produced  under  nature", 
if  two  forms  hitherto  reputed  to  be  varieties  be  found  in 
any  degree  sterile  together,  they  are  at  once  ranked  by 
most  naturalists  as  species.  For  Instance,  the  blue  and  red 
pimpernel,  which  are  considered  by  most  botanists  as 
varieties,  are  said  by  Gartner  to  be  quite  sterile  when 
crossed,  and  he  consequently  ranks  them  as  undoubted 


302 


FERTILITY  OF  VARIETIES 

species.  If  we  thus  argue  in  a  circle,  the  fertility  of  all 
varieties  produced  under  nature  will  assuredly  have  to  be 

^'ifwe  turn  to  varieties,  produced,  or  supposed  to  have 
been  produced,  under  domestication,  we  aie  still  involvei 
in  some  doubt.  For  when  it  is  stated,  for  instance, 
that  certain  South  American  indigenous  domestic  dogs  do 
not  readily  unite  with  European  dogs,  the  explanation 
which  will  occur  to  every  one,  and  probably  the  true  one, 
is  that  they  are  descended  from  aboriginally  distinct 
species.  Nevertheless  the  perfect  fertility  of  so  many  do¬ 
mestic  races,  differing  widely  from  each  othei  in  appear¬ 
ance,  for  instance,  those  of  the  pigeon,  or  of  the  cabbage, 
is  a  remarkable  fact;  more  especially  when  we  reflect  how 
many  species  there  are,  which,  though  resembling  each 
other  most  closely,  are  utterly  sterile  when  intercrossed. 
Several  considerations,  however,  render  the  fertility  ot  do¬ 
mestic  varieties  less  remarkable.  In  the  first  place,  it  may 
be  observed  that  the  amount  of  external  difference  between 
two  species  is  no  sure  guide  to  their  degree  of  mutual 
sterility,  so  that  similar  differences  in  the  case  of  varieties 
would  be  no  sure  guide.  It  is  certain  that  with  species  the 
cause  lies  exclusively  in  differences  in  their  sexual  consti¬ 
tution  Now  the  varying  conditions  to  which  domesticated 
aniinais  and  cultivated  plants  have  been  subjected,  have 
had  so  little  tendency  toward  modifying  the.  reproductive 
system  in  a  manner  leading  to  mutual  sterility,  that  we 
have  good  grounds  for  admitting  the  directly  opposite  doc¬ 
trine  of  Pallas,  namely,  that  such  conditions  generally 
eliminate  this  tendency;  so  that  the  domesticated  descend¬ 
ants  of  species,  which  in  their  natural  state  probably  won  d 
have  been  in  some  degree  sterile  when  crossed,  become  per¬ 
fects  fertile  together.  With  plants.,  so  far  is  cultivation 
from  giving  a  tendency  toward  sterility  between  distinct 
species,  that  in  several  well-authenticated  cases  already 
alluded  to,  certain  plants  have  been  affected  in  an  opposite 
manner,  for  they  have  become  self-impotent,  while,  still 
retaining  the  capacity  of  fertilizing,  and.  being  fertilized 
by,  other  species.  If  the  Pallasian  doctrine  of  the  elimi¬ 
nation  of  sterility  through  long-continued  domestication  be 
admitted,  and  it  can  hardly  be  rejected,  it  becomes  in  the 
highest  degree  improbable  that  similar  conditions  long-con- 


WHEN  CROSSED. 


303 


tinued  should  likewise  induce  this  tendency ;  though  in 
certain  cases,  with  species  having  a  peculiar  constitution, 
sterility  might  occasionally  be  thus  caused.  Thus,  as  I 
believe,  we  can  understand  why,  with  domesticated  ani¬ 
mals,  varieties  have  not  been  produced  which  are  mutually 
sterile;  and  why  with  plants  only  a  few  such  cases,  imme¬ 
diately  to  be  given,  have  been  observed. 

The  real  difficulty  in  our  present  subject  is  not,  as  it 
appears  to.  me,  why  domestic  varieties  have  not  become 
mutually  infertile  when  crossed,  but  why  this  has  so 
generally  occurred  with  natural  varieties,  as  soon  as 
they  have  been  permanently  modified  in  a  sufficient  de¬ 
gree  to  take  rank  as  species.  We  are  far  from  precisely 
knowing  the  cause;  nor  is  this  surprising,  seeing  how 
profoundly  ignorant  we  are  in  regard  to  the  normal 
and  abnormal  action  of  the  reproductive  system.  But 
we  can  see  that  species,  owing  to  their  struggle  for  exist¬ 
ence  with  numerous  competitors,  will  have  been  exposed 
during  long  periods  of  time  to  more  uniform  conditions, 
than  have  domestic  varieties;  and  this  may  well  make 
a  wide  difference  in  the  result.  For  we  know  how 
commonly  wild  animals  and  plants,  when  taken  from 
their  natural  conditions  and  subjected  to  captivity, 
are  rendered  sterile ;  and  the  reproductive  functions 
of  organic  beings  which  have  always  lived  under  natural 
conditions  would  probably  in  like  manner  be  emi¬ 
nently  sensitive  to  the  influence  of  an  unnatural  cross. 
Domesticated  productions,  on  the  other  hand,  which,  as 
shown  by  the  mere  fact  of  their  domestication,  were  not 
originally  highly  sensitive  to  changes  in  their  conditions  of 
life,  and  which  can  now  generally  resist  with  undimin¬ 
ished  fertility  repeated  changes  of  conditions,  might  be 
expected  to.  produce  varieties,  which  would  be  little  liable 
to  have  their  reproductive  powers  injuriously  affected  by 
the  act  of  crossing  with  other  varieties  which  had  origi¬ 
nated  in  a  like  manner. 

I  have  as  yet  spoken  as  if  the  varieties  of  the  same  species 
were  invariably  fertile  when  intercrossed.  But  it  is  impos¬ 
sible  to  resist  the  evidence  of  the  existence  of  a  certain 
amount  of  sterility  in  the  few  following  cases,  which  I  will 
briefly  abstract.  The  evidence  is  at  least  as  good  as  that 
from  which  we  believe  in  the  sterility  of  a  multitude  of 


304 


FERTILITY  OF  VARIETIES 


species.  The  evidence  is  also  derived  from  hostile  wit¬ 
nesses,  who  in  all  other  ca«es  consider  fertility  and  sterility 
as  safe  criterions  of  specific  distinction.  .  Gartner  kept, 
during  several  years,  a  dwarf  kind  of  maize  with  yellow 
seeds,  and  a  tall  variety  with  red  seeds  growing  near  each 
other  in  his  garden;  and  although  these  plants  have  sepa- 
ated  sexes,  they  never  naturally  crossed.  He  then  fertil¬ 
ized  thirteen  flowers  of  the  one  kind  with  pollen  of  the 
other;  but  only  a  single  head  produced  any  seed,  and  this 
one  head  produced  only  five  grains.  Manipulation  in  this 
case  could  not  have  been  injurious,  as  the  plants  have  sepa¬ 
rated  sexes.  Ho  one,  I  believe,  has  suspected  that  these 
varieties  of  maize  are  distinct  species;  and.it  is  important; 
to  notice  that  the  hybrid  plants  thus  raised  were  them¬ 
selves  perfectly  fertile;  so  that  even  Gartner  did  not  ven¬ 
ture  to  consider  the  two  varieties  as  specifically  distinct. 

Girou  de  Buzareingues  crossed  three  varieties  of  gourd, 
which  like  the  maize  has  separate  sexes,  and  he  asserts  that 
their  mutual  fertilization  is  by  so  much  the  less  easy  as 
their  differences  are  greater.  How  far  these  experiments 
may  be  trusted,  I  know  not;  but  the  forms  experimented 
on  are  ranked  by  Sageret,  who  mainly  founds  his  classifi¬ 
cation  by  the  test  of  infertility,  as  varieties,  and  Naudin 
has  come  to  the  same  conclusion. 

The  following  case  is  far  more  remarkable,  and  seems  at 
first  incredible;  but  it  is  the  result  of  an  astonishing  num¬ 
ber  of  experiments  made  during  many  years  on  nine  species 
of  Verbascum,  by  so  good  an  observer  and  so  hostile  a  wit¬ 
ness  as  Gartner:  namely,  that  the  yellow  and  white  varie¬ 
ties  when  crossed  produce  less  seed  than  the  similarly 
colored  varieties  of  the  same  species.  Moreover,  he  asserts 
that,  when  yellow  and  white  varieties  of  one  species  are 
crossed  with  yellow  and  white  varieties  of  a  distinct 
species,  more  seed  is  produced  by  the  crosses  between  the 
similarly  colored  flowers,  than  between  those  which  are  dif¬ 
ferently  colored.  Mr.  Scott  also  has  experimented  on  the 
species  and  varieties  of  Verbascum;  and  although  unable 
to  confirm  Gartner’s  results  on  the  crossing  of  the  distinct 
species,  he  finds  that  the  dissimilarly,  colored  varieties  of 
the  same  species  yield  fewer  seeds,  in  the  proportion  of 
eighty-six  to  100,  than  the  similarly  colored  varieties.  Yet 
these  varieties  differ  in  no  respect,  except  in  the  color  of 


WHEN  CROSSED.  305 

their  flowers;  and  one  variety  can  sometimes  be  raised 
from  the  seed  of  another.  « 

Kdlreuter,  whose  accuracy  has  been  confirmed  by 
every  subsequent  observer,  has  proved  the  remarkable 
fact  that  one  particular  variety  of  the  common  tobacco 
was  more  fertile  than  the  other  varieties,  when  crossed 
with  a  widely  distinct  species.  He  experimented  on  five 
forms  which  are  commonly  reputed  to  be  varieties,  and 
which  he  tested  by  the  severest  trial,  namely,  by  recipro¬ 
cal  crosses,  and  he  found  their  mongrel  offspring  perfectly 
fertile.  But  one  of  these  five  varieties,  when  used  either 
as  the  father  or  mother,  and  crossed  with  the  Nico- 
tiana  glutinosa,  always  yielded  hybrids  not  so  sterile  as 
those  which  were  produced  from  the  four  other  varieties 
when  crossed  with  N.  glutinosa.  Hence,  the  reproductive 
system  of  this  one  variety  must  have  been  in  some  manner 
and  in  some  degree  modified. 

From  these  facts  it  can  no  longer  be  maintained  that 
varieties  when  crossed  are  invariably  quite  fertile.  From 
the  great  difficulty  of  ascertaining  the  infertility  of  varie~ 
ties  in  a  state  of  nature,  for  a  supposed  variety,  if  proved 
to  be  infertile  in  any  degree,  would  almost  universally  be 
ranked  as  a  species;  from  man  attending  only  to  external 
characters  in  his  domestic  varieties,  and  from  such 
varieties  not  having  been  exposed  for  very  long  periods  to 
uniform  conditions  of  life;  from  these  several  considera¬ 
tions  we  may  conclude  that  fertility  does  not  constitute  a 
fundamental  distinction  between  varieties  and  species  when 
crossed.  The  general  sterility  of  crossed  species  may 
safely  be  looked  at,  not  as  a  special  acquirement  or  endow¬ 
ment,  but  as  incidental  on  changes  of  an  unknown  nature 
in  their  sexual  elements. 

HYBRIDS  AND  MONGRELS  COMPARED,  INDEPENDENT! Tr 

OF  THEIR  FERTILITY. 

Independently  of  the  question  of  fertility,  the  offspring 
of  species  and  of  varieties  when  crossed  may  be  compared 
in  several  other  respects.  Gartner,  whose  strong  wish  it 
was  to  draw  a  distinct  line  between  species  and  varieties, 
could  find  very  few,  and,  as  it  seems  to  me,  quite  unim¬ 
portant  differences  between  the  so-called  hybrid  offspring 


306  HYBRIDS  AND  MONGRELS  COMPARED. 


of  species,  and  the  so-called  mongrel  offspring  of  varieties. 
And,  on  vthe  other  hand,  they  agree  most  closely  in  many 
important  respects. 

I  shall  here  discuss  this  subject  with  extreme  brevity. 
The  most  important  distinction  is,  that  in  the  first  genera¬ 
tion  mongrels  are  more  variable  than  hybrids;  but  Gartner 
admits  that  hybrids  from  species  which  have  long  been  cul¬ 
tivated  are  often  variable  in  the  first  generation;  and  I 
have  myself  seen  striking  instances  of  this  fact.  Gartner 
further  admits  that  hybrids  between  very  closely  allied 
species  are  more  variable  than  those  from  very  distinct 
species;  and  this  shows  that  the  difference  in  the  degree  of 
variability  graduates  away.  When  mongrels  and  the  more 
fertile  hybrids  are  propagated  for  several  generations,  an 
extreme  amount  of  variability  in  the  offspring  in  both 
cases  is  notorious;  but  some  few  instances  of  both  hybrids 
and  mongrels  long  retaining  a  uniform  character  could  be 
given.  The  variability,  however,  in  the  successive  gener¬ 
ations  of  mongrels  is,  perhaps,  greater  than  in  hybrids. 

This  greater  variability  in  mongrels  than  in  hybrids 
does  not  seem  at  all  surprising.  For  the  parents  of 
mongrels  are  varieties,  and  mostly  domestic  varieties 
(very  few  experiments  having  been  tried  on  natural  varie¬ 
ties),  and  this  implies  that  there  has  been  recent  variabil¬ 
ity,  which  would  often  continue  and  would  augment 
that  arising  from  the  act  of  crossing.  The  slight 
variability  of  hybrids  in  the  first  generation,  in  contrast 
with  that  in  the  succeeding  generations,  is  a  curious  fact 
and  deserves  attention.  For  it  bears  on  the  view  which  I 
have  taken  of  one  of  the  causes  of  ordinary  variability, 
namely,  that  the  reproductive  system,  from  being  eminently 
sensitive  to  changed  conditions  of  life,  fails  under  these 
circumstances  to  perform  its  proper  function  of  producing 
offspring  closely  similar  in  all  respects  to  the  parent  form. 
Now,  hybrids  in  the  first  generation  are  descended  from 
species  (excluding  those  long  cultivated)  which  have  not 
had  their  reproductive  systems  in  any  way  affected,  and 
they  are  not  variable;  but  hybrids  themselves  have  the  re¬ 
productive  systems  seriously  affected  and  their  descendants 
are  highly  variable. 

But  to  return  to  our  comparison  of  mongrels  and 
hybrids:  Gartner  states  that  mongrels  are  more  liable , 


HYBRIDS  AND  MONGRELS  COMPARED.  3q7 

than  hybrids  to  revert  to  either  parent  form;  but  this,  if  it 
be  true,  is  certainly  only  a  difference  in  degree.  More¬ 
over,  Gartner  expressly  states  that  the  hybrids  from  long 
cultivated  plants  are  more  subject  to  reversion  than 

lybuds  fiom  species  in  their  natural  state;  and  this  prob¬ 
ably  explains  the  singular  difference  in  the  results  arrived 
at  by  different  observers.  Thus  Max  Wichura  doubts 
whether  hybrids  ever  revert  to  their  parent  forms,  and  he 
experimented  on  uncultivated  species  of  willows,  while 
Naudin,  on  the  other  hand,  insists  in  the  strongest  terms 
on  the  almost  universal  tendency  to  reversion  in  hybrids 
and  he  experimented  chiefly  on  cultivated  plants.  Gartner 
further  states  that  when  any  two  species,  although  most 
closely  allied  to  each  other,  are  crossed  with  a  third  species, 
the  hybiids  are  widely  different  from  each  other;  whereas 
if  two  \ery  distinct  varieties  of  one  species  are  crossed  with 
another  species,  the  hybrids  do  not  differ  much.  But  this 
conclusion,  as  far  as  I  can  make  out,  is  founded  on  a 
single  experiment,  and  seems  directly  opposed  to  the 
results  of  several  experiments  made  by  Kolreuter. 

Such  alone  are  the  unimportant  differences  which 
Gaitnei  is  able  to  point  out  between  hybrid  and  mongrel 
plants.  On  the  other  hand,  the  degrees  and  kinds  of  re¬ 
semblance  in  mongrels  and  in  hybrids  to  their  respective 
parents,  more  especially  in  hybrids  produced  from  nearly 
related  species,  follow,  according  to  Gartner,  the  same 
laws.  When  two  species  are  crossed,  one  has  sometimes  a 
prepotent  power  of  impressing  its  likeness  on  the  hybrid, 
bo  I  believe  it  to  be  with  varieties  of  plants;  and  with  ani¬ 
mals,  one  variety  certainly  often  has  this  prepotent  power 
over  another  variety.  Hybrid  plants  produced  from  a 
lecipiocal  cross  generally  resemble  each  other  closely,  and 
so  it  is  with  mongrel  plants  from  a  reciprocal  cross.  Both 
hybrids  and  mongrels  can  be  reduced  to  either  pure  parent 

foim  by  repeated  crosses  in  successive  generations  with 
either  parent. 

These  several  remarks  are  apparently  applicable  to  ani¬ 
mals,  but  the  subject  is  here  much  complicated,  partly 
owing  to  the  existence  of  secondary  sexual  characters,  but 
more  especially  owing  to  prepotency  in  transmitting  like¬ 
ness  running  more  strongly  in  one' sex  than  in  the  other, 
both  when  one  species  is  crossed  with  another  and  when 


308  HYBRIDS  AND  MONGRELS  COMPARED. 

one  variety  is  crossed  with  another  variety.  For  instance, 
X  think  those  authors  are  right  who  maintain  that  the  ass 
has  a  prepotent  power  over  the  horse,  so  that  both  the 
mule  and  the  hinny  resemble  more  closely  the  ass  than  the 
horse;  but  that  the  prepotency  runs  more  strongly  in  the 
male  than  in  the  female  ass,  so  that  the  mule,  which  is  an 
offspring  of  the  male  ass  and  mare,  is  more  like  an  ass  than 
is  the  hinny,  which  is  the  offspring  of  the  female  ass  and 
stallion. 

Much  stress  has  been  laid  by  some  authors  on  the  sup¬ 
posed  fact,  that  it  is  only  with  mongrels  that  the  offspring 
are  not  intermediate  in  character,  but  closely  resemble  one 
of  their  parents;  but  this  does  sometimes  occur  with 
hybrids,  yet  I  grant  much  less  frequently  than  with  mon¬ 
grels.  Looking  to  the  cases  which  I  have  collected  of 
cross-bred  animals  closely  resembling  one  parent,  the  re¬ 
semblances  seem  chiefly  confined  to  characters  almost  mon¬ 
strous  in  their  nature,  and  which  have  suddenly  appeared 
— such  as  albinism,  melanism,  deficiency  of  tail  or  horns, 
or  additional  fingers  and  toes;  and  do  not  relate  to  char¬ 
acters  which  have  been  slowly  acquired  through  selection. 
A  tendency  to  sudden  reversions  to  the  perfect  character 
of  either  parent  would,  also,  be  much  more  likely  to  occur 
with  mongrels,  which  are  descended  from  varieties  often 
suddenly  produced  and  semi-monstrous  in  character,  than 
with  hybrids,  which  are  descended  from  species  slowly  and 
naturally  produced.  On  the  whole,  I  entirely  agree  with 
Dr.  Prosper  Lucas,  who,  after  arranging  an  enormous 
body  of  facts  with  respect  to  animals,  comes  to  the  con¬ 
clusion  that  the  laws  of  resemblance  of  the  child  to  its 
parents  are  the  same,  whether  the  two  parents  differ  little 
or  much  from  each  other,  namely,  in  the  union  of  individ¬ 
uals  of  the  same  variety,  or  of  different  varieties,  or  of 
distinct  species. 

Independently  of  the  question  of  fertility  and  sterility, 
in  all  other  respects  there  seems  to  be  a  general  and  close 
similarity  in  the  offspring  of  crossed  species,  and  of  crossed 
varieties”  If  we  look  at  species  as  having  been  specially 
created,  and  at  varieties  as  having  been  produced  by  sec¬ 
ondary  laws,  this  similarity  would  be  an  astonishing  fact. 
But  it  harmonizes  perfectly  with  the  view  that  there  is  no 
essential  distinction  between  species  and  varieties. 


SUMMARY. 


309 


SUMMARY  OF  CHAPTER. 

First  crosses  between  forms,  sufficiently  distinct  to  be 
ranked  as  species,  and  their  hybrids,  are  very  generally, 
but  not  universally,  sterile.  The  sterility  is  of  all  degrees, 
and  is  often  so  slight  that  the  most  careful  experimental¬ 
ists  have  arrived  at  diametrically  opposite  conclusions  iu 
ranking  forms  by  this  test.  The  sterility  is  innately  vari¬ 
able  in  individuals  of  the  same  species,  and  is  eminently, 
susceptible  to  action  of  favorable  and  unfavorable  condi¬ 
tions.  The  degree  of  sterility  does  not  strictly  follow 
systematic  affinity,  but  is  governed  by  several  curious  and 
complex  laws.  It  is  generally  different,  and  sometimes 
widely  different  in  reciprocal  crosses  between  the  same  two 
species.  It  is  not  always  equal  in  degree  in  a  first  cross 
and  in  the  hybrids  produced  from  this  cross. 

In  the  same  manner  as  in  grafting  trees,  the  capacity  in 
one  species  or  variety  to  take  on  another,  is  incidental  on 
differences,  generally  of  an  unknown  nature,  in  their  vege¬ 
tative  systems,  so  in  crossing,  the  greater  or  less  facility  of 
one  species  to  unite  with  another  is  incidental  on  unknown 
differences  in  their  reproductive  systems.  There  is  no 
more  reason  to  think  that  species  have  been  specially  en¬ 
dowed  with  various  degrees  of  sterility  to  prevent  their 
crossing  and  blending  in  nature,  than  to  think  that  trees 
have  been  specially  endowed  with  various  and  somewhat 
analogous  degrees  of  difficulty  in  being  grafted  together  in 
order  to  prevent  their  inarching  in  our  forests. 

The  sterility  of  first  crosses  and  of  their  hybrid  progeny 
has  not  been  acquired  through  natural  selection.  In  the 
case  of  first  crosses  it  seems  to  depend  on  several  circum¬ 
stances;  in  some  instances  in  chief  part  on  the  early  death 
of  the  embryo.  In  the  case  of  hybrids,  it  apparently  de¬ 
pends  on  their  whole  organization  having  been  disturbed 
by  being  compounded  from  two  distinct  forms;  the  ster¬ 
ility  being  closely  allied  to  that  which  so  frequently  affects 
pure  species,  when  exposed  to  new  and  unnatural  con¬ 
ditions  of  life.  He  who  will  explain  these  latter  cases  will 
be  able  to  explain  the  sterility  of  hybrids.  This  view  is 
strongly  supported  by  a  parallelism  of  another  kind: 
namely,  that,  firstly,  slight  changes  in  the  conditions  of 
life  add  to  the  vigor  and  fertility  of  all  organic  beings;  and 


310 


SUMMARY. 


secondly,  that  the  crossing  of  forms,  which  have  been  ex¬ 
posed  to  slightly  different  conditions  of  life,  or  which  have 
varied,  favors  the  size,  vigor  and  fertility  of  their  offspring. 
The  facts  given  on  the  sterility  of  the  illegitimate  unions 
of  dimorphic  and  trimorphic  plants  and  of  their  illegitimate 
progeny,  perhaps  render  it  probable  that  some  unknown 
bond  in  all  cases  connects  the  degree  of  fertility  of  first 
unions  with  that  of  their  offspring.  The  consideration  of 
these  facts  on  dimorphism,  as  well  as  of  the  results  of  re¬ 
ciprocal  crosses,  clearly  leads  to  the  conclusion  that  the 
primary  cause  of  the  sterility  of  crossed  species  is  confined 
to  differences  in  their  sexual  elements.  But  why,  in  the 
case  of  distinct  species,  the  sexual  elements  should  so  gen¬ 
erally  have  become  more  or  less  modified,  leading  to  their 
mutual  infertility,  we  do  not  know;  but  it  seems  to  stand 
in  some  close  relation  to  species  having  been  exposed  for 
long  periods  of  time  to  nearly  uniform  conditions  of  life. 

It  is  not  surprising  that  the  difficulty  in  crossing  any 
two  species,  and  the  sterility  of  their  hybrid  offspring, 
should  in  most  cases  correspond,  even  if  due  to  distinct 
causes:  for  both  depend  on  the  amount  of  difference  be¬ 
tween  the  species  which  are  crossed.  Nor  'it  surprising 
that  the  facility  of  effecting  a  first  cross,  and  the  fertility 
of  the  hybrids  thus  produced,  and  the  capacity  of  being 
grafted  together — though  this  latter  capacity  evidently 
depends  on  widely  different  circumstances — should  all  run, 
to  a  certain  extent,  parallel  with  the  systematic  affinity  of 
the  forms  subjected  to  experiment;  for  systematic  affinity 
includes  resemblances  of  all  kinds. 

First  crosses  between  forms  known  to  be  varieties,  or 
sufficiently  alike  to  be  considered  as  varieties,  and  their 
mongrel  offspring,  are  very  generally,  but  not,  as  is  so 
often  stated,  invariably  fertile.  Nor  is  this  almost  uni¬ 
versal  and  perfect  fertility  surprising,  when  it  is  remem¬ 
bered  how  liable  we  are  to  argue  in  a  circle  with  respect  to 
varieties  in  a  state  of  nature;  and  when  we  remember  that 
the  greater  number  of  varieties  have  been  produced  under 
domestication  by  the  selection  of  mere  external  differences, 
and  that  they  have  not  been  long  exposed  to  uniform  con¬ 
ditions  of  life.  It  should  also  be  especially  kept  in  mind, 
that  long-continued  domestication  tends  to  eliminate  ster¬ 
ility,  and  is  therefore  little  likely  to  induce  this  same 


SUMMARY. 


311 


quality.  Independently  of  the  question  of  fertility, 
in  all  other  respects  there  is  the  closest  general  resemblance 
between  hybrids  and  mongrels,  in  their  variability,  in  their 
power  of  absorbing  each  other  by  repeated  crosses,  and  in 
their  inheritance  of  characters  from  both  parent-forms. 
Finally,  then,  although  we  are  as  ignorant  of  the  precise 
cause  of  the  sterility  of  first  crosses  and  of  hybrids  as  we 
are  why  animals  and  plants  removed  from  their  natural 
conditions  become  sterile,  yet  the  facts  given  in  this 
chapter  do  not  seem  to  me  opposed  to  the  belief  tha« 
species  aboriginally  existed  as  varieties. 


312 


IMPERFECTION  OF  TEE 


CHAPTER  X. 

ON  THE  IMPERFECTION  OF  THE  GEOLOGICAL  RECORD. 

On  the  absence  of  intermediate  varieties  at  the  present  day— On  the 
nature  of  extinct  intermediate  varieties;  on  their  number— On 
the  lapse  of  time,  as  inferred  from  the  rate  of  denudation  and  or 
deposition — On  the  lapse  of  time  as  estimated  by  years  On  the 
poorness  of  our  palaeontological  collections — On  the  intermittence 
of  geological  formations— On  the  denudation  of  granitic  areas— 
On  the  absence  of  intermediate  varieties  in  any  one  formation— 
On  the  sudden  appearance  of  groups  of  species — On  their  sudden 
appearance  in  the  lowest  known  fossiliferous  strata  Antiquity 
of  the  habitable  earth. 

1^  the  sixth  chapter  I  enumerated  the  chief  objections 
which  might  be  justly  urged  against  the  views  maintained 
in  this  volume.  Most  of  them  have  now  been  discussed. 
One,  namely,  the  distinctness  of  specific  forms  and  their 
not  being  blended  together  by  innumerable  transitional 
links,  is  a  very  obvious  difficulty.  I  assigned  reasons  why 
such  links  do  not  commonly  occur  at  the  present  day  under 
the  circumstances  apparently  most  favorable  for  their  pres¬ 
ence,  namely,  on  an  extensive  and  continuous  area  with 
graduated  physical  conditions.  I  endeavored  to  show,  that 
the  life  of  each  species  depends  in  a  more  important  manner 
on  the  presence  of  other  already  defined  organic  forms,  than 
on  climate,  and,  therefore,  that  the  really  governing  condi¬ 
tions  of  life  do  not  graduate  away  quite  insensibly  like 
heat  or  moisture.  I  endeavored,  also,  to  show  that  inter¬ 
mediate  varieties,  from  existing  in  lesser  numbers  than 
the  forms  which  they  connect,  will  generally  be  beaten  out 
and  exterminated  during  the  course  of  further  modifica¬ 
tion  and  improvement.  The  main  cause,  however,  of 
innumerable  intermediate  links  not  now  occurring  every¬ 
where  throughout  nature,  depends  on  the  very  process  of 
natural  selection,  through  which  new  varieties  continually 
take  the  places  of  and  supplant  their  parent-forms.  But 


GEOLOGICAL  RECORD. 


313 


just  in  proportion  as  this  process  of  extermination  has 
acted  on  an  enormous  scale,  so  must  the  number  of  inter¬ 
mediate  varieties,  which  have  formerly  existed,  be  truly 
enormous.  Why  then  is  not  every  geological  formation 
and  every  stratum  full  of  such  intermediate  links?  Geo¬ 
logy  assuredly  does  not  reveal  any  such  finely-graduated 
organic  chain;  and  this,  perhaps,  is  the  most  obvious  and 
serious  objection  which  can  be  urged  against  the  theory. 
The  explanation  lies,  as  I  believe,  in  the  extreme  imper¬ 
fection  of  the  geological  record. 

In  the  first  place,  it  should  always  be  borne  in  mind 
what  sort  of  intermediate  forms  must,  on  the  theory,  have 
formerly  existed.  I  have  found  it  difficult,  when  looking 
at  any  two  species,  to  avoid  picturing  to  myself  forms 
directly  intermediate  between  them.  But  this  is  a  wholly 
false  view;  we  should  always  look  for  forms  intermediate 
between  each  species  and  a  common  but  unknown  pro¬ 
genitor;  and  the  progenitor  will  generally  have  differed,  in 
some  respects  from  all  its  modified  descendants.  To  give 
a  simple  illustration:  the  fantail  and  pouter  pigeons  are 
both  descended  from  the  rock-pigeon;  if  we  possessed  all 
the  intermediate  varieties  which  have  ever  existed,  we 
should  have  an  extremely  close  series  between  both  and 
the  rock-pigeon;  but  we  should  have  no  varieties  directly 
intermediate  between  the  fantail  and  pouter;  none,  for 
instance,  combining  a  tail  somewhat  expanded  with  a  crop 
somewhat  enlarged,  the  characteristic  features  of  these  two 
breeds.  These  two  breeds,  moreover,  have  become  so 
much  modified,  that,  if  we  had  no  historical  or  indirect 
evidence  regarding  their  origin,  it  would  not  have  been 
possible  to  have  determined,  from  a  mere  comparison  of 
their  structure  with  that  of  the  rock-pigeon,  0.  livia, 
whether  they  had  descended  from  this  species  or  from 
some  other  allied  form,  such  as  C.  oenas. 

So,  with  natural  species,  if  we  look  to  forms  very  dis¬ 
tinct,  for  instance  to  the  horse  and  tapir,  we  have  no 
reason  to  suppose  that  links  directly  intermediate  between 
them  ever  existed,  but  between  each  and  an  unknown 
common  parent.  The  common  parent  will  have  had  in  its 
whole  organization  much  general  resemblance  to  the  tapir 
and  to  the  horse;  but  in  some  points  of  structure  may 
have  differed  considerably  from  both,  even  perhaps  more 


314 


THE  LAPSE  OF  TIME. 


than  they  differ  from  each  other.  Hence,,  in  all  such 
cases,  we  should  be  unable  to  recognize  the  parent- form  of 
any  two  or  more  species,  even  if  we  closely  compared  the 
structure  of  the  parent  with  that  of  its  modified  descend¬ 
ants,  unless  at  the  same  time  we  had  a  nearly  perfect  chain 
of  the  intermediate  links. 

It  is  just  possible,  by  the  theory,  that  one  of  two 
living  forms  might  have  descended  from  the  other;  for 
instance,  a  horse  from  a  tapir ;  and  in  this  case  direct 
intermediate  links  will  have  existed  between  them.  But 
such  a  case  would  imply  that  one  form  had  remained 
for  a  very  long  period  unaltered,  while  its  descend¬ 
ants  had  undergone  a  vast  amount  of  change;  and  the 
principle  of  competition  between  organism  and  organism, 
between  child  and  parent,  will  render  this  a  very  rare 
event;  for  in  all  cases  the  new  and  improved  forms  of  life 
tend  to  supplant  the  old  and  unimproved  forms. 

By  the  theory  of  natural  selection  all  living  species  have 
been  connected  with  the  parent-species  of  each  genus,  by 
differences  not  greater  than  we  see  between  the  natural  and 
domestic  varieties  of  the  same  species  at  the  present  day; 
and  these  parent-species,  now  generally  extinct,  have  in 
their  turn  been  similarly  connected  with  more  ancient 
forms;  and  so  on  backward,  always  converging  to  the 
common  ancestor  of  each  great  class.  So  that  the  number 
of  intermediate  and  transitional  links,  between  all  living 
and  extinct  species,  must  have  been  inconceivably  great. 
But  assuredly,  if  this  theory  be  true,  such  have  lived  upon 
the  earth. 

ON  THE  LAPSE  OP  TIME,  AS  INFERRED  FROM  THE  RATE 
OF  DEPOSITION  AND  EXTENT  OF  DENUDATION. 

Independently  of  our  not  finding  fossil  remains  of  such 
infinitely  numerous  connecting  links,  it  may  be  objected 
that  time  cannot  have  sufficed  for  so  great  an  amount  of 
organic  change,  all  changes  having  been  effected  slowly. 
It  is  hardly  possible  for  me  to  recall  to  the  reader  who  is 
not  a  practical  geologist,  the  facts  leading  the  mind  feebly 
to  comprehend  the  lapse  of  time.  He  who  can  read  Sir 
Charles  Ly ell's  grand  work  on  the  Principles  of  Geology, 
which  the  future  historian  will  recognize  as  having  pro* 


TEE  LAPSE  OF  TIME.  3^ 

duced  a  1  evolution  in  natural  science,  and  yet  does  not 
admit  now  \ast  have  been  the  past  periods  of  time,  may  at 
once  close  this  volume.  Not  that  it  suffices  to  study  the 
.riinciples  of  Geology,  or  to  read  special  treatises  by  differ¬ 
ent  observeis  on  separate  formations,  and  to  mark  how 
eacli  author  attempts  to  give  an  inadequate  idea  of  the 
duiation  of.  each  formation,  or  even  of  each  stratum.  We 
can  best  gain  some  idea  of  past  time  by  knowing  the  agen¬ 
cies  at  work;  and  learning  how  deeply  the  surface  of&the 
land  has  been  denuded,  and  how  much  sediment  has  been 
deposited.  As  Lyell  has  well  remarked,  the  extent  and 
thickness  of  our  sedimentary  formations  are  the  result  and 
the  measure  of  the  denudation  which  the  earth/ s  crust  has 
elsewhere  undergone.  Therefore  a  man  should  examine 
for  himself  the  great  piles  of  superimposed  strata,  and 
watch  the  rivulets  bringing  down  mud,  and  the  waves 
wearing  away  the  sea-cliffs,  in  order  to  comprehend  some¬ 
thing  about  the  duration  of  past  time,  the  monuments  of 
which  we  see  all  around  us. 

It  is  good  to  wander  along  the  coast,  when  formed  of 
moderately  hard  rocks,  and  mark  the  process  of  degrada¬ 
tion.  .The  tides  in  most  cases  reach  the  cliffs  only  for  a 
short  time  twice  a  day,  and  the  waves  eat  into  them  only 
when  they  are  charged  with  sand  or  pebbles;  for  there  is 
good  evidence  that  pure  water  effects  nothing  in  wearing 
away  rock.  At  last  the  base  of  the  cliff  is  undermined, 
huge  fragments  fall  down,  and  these,  remaining  fixed,  have 
to  be  worn  away  atom  by  atom,  until  after  being  reduced 
in  size  they  can  be  rolled  about  by  the  waves,  and  then 
they  are  more  quickly  ground  into  pebbles,  sand  or  mud. 
But  .  how  often  do  we  see  along  the  bases  of  re¬ 
treating.  cliffs  rounded  boulders,  all  thickly  clothed 
by  marine  productions,  showing  how  little  they  are 
abraded,  and  how  seldom  they  are  rolled  about!  More¬ 
over,  if.  we  follow  for  a  few  miles  any  line  of 
rocky  cliff,  which  is  undergoing  degradation,  wre  find  that 
it  is  only  here  and  there,  along  a  short  length  or  round  a 
promontory,  that  the  cliffs  are  at  the  present  time  suffering. 

I  he  appearance  of  the  surface  and  the  vegetation  show  that 
elsewhere  years  have  elapsed  since  the  waters  washed  their 
base. 

We  have,  however,  x’ecently  learned  from  the  obserya- 


TI1E  LAPSE  OF  TIME. 


316 

tions  of  Ramsay,  in  the  van  of  many  excellent  observers— 
of  Jukes,  Geikie,  Croll  and  others,  that  subaerial  degrada¬ 
tion  is  a  much  more  important  agency  than  coast-action 
or  the  power  of  the  waves.  The  whole  surface  of  the  land 
is  exposed  to  the  chemical  action  of  the  air  and  of  the  ram- 
water,  with  its  dissolved  carbonic  acid,  and  in  colder  coun¬ 
tries  to  frost;  the  disintegrated  matter  is  carried  down  even 
gentle  slopes  during  heavy  rain,  and  to  a  greater  extent 
than  might  be  supposed,  especially  m  and  districts,  by  the 
wind:  it  is  then  transported  by  the  streams  and  rivers, 
which,  when  rapid  deepen  their  channels,  and  triturate  the 
fragments.  On  a  rainy  day,  even  in  a  gently  undulating 
country,  we  see  the  effects  of  subaenal  degradation  m  the 
muddy  rills  which  flow  down  every  slope.  Messrs.  Ramsay 
and  Whitaker  have  shown,  and  the  observation  is  a  most 
striking  one,  that  the  great  lines  of  escarpment  m  the 
Wealden  district  and  those  ranging  across  England,  which 
formerly  were  looked  at  as  ancient  sea-coasts,  can  not  have 
been  thus  formed,  for  each  line  is  composed  of  one  and  the 
same  formation,  while  our  sea-cliffs  are  everywhere  formed 
by  the  intersection  of  various  formations.  This  being  the 
case,  we  are  compelled  to  admit  that  the  escarpments  owe 
their  origin  in  chief  part  to  the  rocks  of  which  they  are 
composed,  having  resisted  subaerial  denudation  better 
than  the  surrounding  surface;  this  surface  consequently 
has  been  gradually  lowered,  with  the  lines  of  harder  rock 
left  projecting.  Nothing  impresses  the  mind  with  the  vast 
duration  of  time,  according  to  our  ideas  of  time,  more 
forcibly  than  the  conviction  thus  gained  that  subaenal 
agencies,  which  apparently  have  so  little  power,  and  which 
seem  to  work  so  slowly,  have  produced  great  results. 

When  thus  impressed  with  the.  slow  -rate  at  which  the 
land  is  worn  away  through  subaerial  and  littoral  action,  it 
is  good,  in  order  to  appreciate  the  past  duration  of  time, 
to  consider,  on  the  one  hand,  the  masses  of  rock  which 
have  been  removed  over  many  extensive  areas,  and  on 
the  other  hand  the  thickness  of  our  sedimentary  forma¬ 
tions.  I  remember  having  been  much  struck  when  view¬ 
ing  volcanic  islands,  which  have  ,  been  worn  by  the  waves 
and  pared  all  round  into  perpendicular  cliffs  of  one  01  wo 
thousand  feet  in  height;  for  the  gentle  slope  of  the  lava- 
streams,  due  to  their  formerly  liquid  state,  showed  at  a 


THE  LAPSE  OF  TIME. 


317 


glance  how  far  the  hard,  rocky  beds  had  once  extended 
into  the  open  ocean.  The  same  story  is  told  still  more 
plainly  by  faults — those  great  cracks  along  which  the  strata 
have  been  upheaved  on  one  side,  or  thrown  down  on  the 
other,  to  the  height  or  depth  of  thousands  of  feet;  for  since 
the  crust  cracked,  and  it  makes  no  great  difference  whether 
the  upheaval  was  sudden,  or,  as  most  geologists  now  believe, 
was  slow  and  effected  by  many  starts,  the  surface  of  the 
land  has  been  so  completely  planed  down  that  no  trace  of 
these  vast  dislocations  is  externally  visible.  The  Craven 
fault,  for  instance,  extends  for  upward  of  thirty  miles,  and 
along  this  line  the  vertical  displacement  of  the  strata  varies 
from  600  to  3,000  feet.  Professor  Ramsay  has  published 
an  account  of  a  downthrow  in  Anglesea  of  2,300  feet;  and 
he  informs  me  that  he  fully  believes  that  there  is  one  in 
Merionethshire  of  12,000  feet;  yet  in  these  cases  there  is 
nothing  on  the  surface  of  the  land  to  show  such  prodigious 
movements;  the  pile  of  rocks  on  either  side  of  the  crack 
having  been  smoothly  swept  away. 

On  the  other  hand,  in  all  parts  of  the  world  the  piles  of 
sedimentary  strata  are  of  wonderful  thickness.  In  the 
Cordillera,  I  estimated  one  mass  of  conglomerate  at  ten 
thousand  feet;  and  although  conglomerates  have  probably 
been  accumulated  at  a  quicker  rate  than  finer  sediments, 
yet  from  being  formed  of  worn  and  rounded  pebbles,  each 
of  which  bears  the  stamp  of  time,  they  are  good  to  show 
how  slowly  the  mass  must  have  been  heaped  together. 
Professor  Ramsay  has  given  me  the  maximum  thickness, 
from  actual  measurement  in  most  cases,  of  the  successive 
formations  in  different  parts  of  Great  Britain;  and  this  is 


the  result: 

Feet. 

Palaeozoic  strata  (not  including  igneous  beds) .  57,154 

Secondary  strata .  13,190 

Tertiary  strata .  2,240 


— making  altogether  72,584  feet;  that  is,  very  nearly  thir¬ 
teen  and  three-quarters  British  miles.  Some  of  the  for¬ 
mations,  which  are  represented  in  England  by  thin  beds, 
are  thousands  of  feet  in  thickness  on  the  Continent.  More¬ 
over,  between  each  successive  formation  we  have,  in  the 
opinion  of  most  geologists,  blank  periods  of  enormous 
length.  So  that  the  lofty  pile  of  sedimentary  rocks  in 


318 


TEE  LAPSE  OF  TIME. 


Britain  gives  but  an  inadequate  idea  of  the  time  which  has 
elapsed  during  their  accumulation.  The  consideration  of 
these  various  facts  impresses  the  mind  almost  in  the  same 
manner  as  does  the  vain  endeavor  to  grapple  with  the  idea 
of  eternity. 

Nevertheless  this  impression  is  partly  false.  Mr.  Croll, 
in  an  interesting  paper,  remarks  that  we  do  not  err  “in 
forming  too  great  a  conception  of  the  length  of  “  geological 
periods/'  but  in  estimating  them  by  years.  When  geolo¬ 
gists  look  at  large  and  complicated  phenomena,  and  then 
at  the  figures  representing  several  million  years,  the  two 
produce  a  totally  different  effect  on  the  mind,  and  the 
figures  are  at  once  pronounced  too  small.  In  regard  to 
subaerial  denudation,  Mr.  Croll  shows,  by  calculating  the 
known  amount  of  sediment  annually  brought  down  by 
certain  rivers,  relatively  to  their  areas  of  drainage,  that 
1,000  feet  of  solid  rock,  as  it  became  gradually  disintegrated, 
would  thus  be  removed  from  the  mean  level  of  the  whole 
area  in  the  course  of  six  million  years.  This  seems  an 
astonishing  result,  and  some  considerations  lead  to  the 
suspicion  that  it  may  be  too  large,  but  if  halved  or  quartered 
it  is  still  very  surprising.  Few  of  us,  however,  know  what 
a  million  really  means:  Mr.  Croll  gives  the  following  illus¬ 
tration:  Take  a  narrow  strip  of  paper,  eighty-three  feet 
four  inches  in  length,  and  stretch  it  along  the  wall  of  a 
large  hall;  then  mark  off  at  one  end  the  tenth  of  an  inch. 
This  tenth  of  an  inch  will  represent  one  hundred  years, 
and  the  entire  strip  a  million  years.  But  let  it  be  borne 
in  mind,  in  relation  to  the  subject  of  this  work,  what 
a  hundred  years  implies,  represented  as  it  is  by  a 
measure  utterly  insignificant  in  a  hall  of  the  above 
dimensions.  Several  eminent  breeders,  during  a  single 
lifetime,  have  so  largely  modified  some  of  the  higher 
animals,  which  propagate  their  kind  much  more  slowly 
than  most  of  the  lower  animals,  that  they  have  formed 
what  well  deserves  to  be  called  a  new  sub-breed.  Few  men 
have  attended  with  due  care  to  any  one  strain  for  more 
than  half  a  century,  so  that  a  hundred  years  represents  the 
work  of  two  breeders  in  succession.  It  is  not  to  be  sup¬ 
posed  that  species  in  a  state  of  nature  ever  change  so 
quickly  as  domestic  animals  under  the  guidance  of  method¬ 
ical  selection.  The  comparison  would  be  in  every  way 


THE  LAPSE  OF  TIME . 


319 


fairer  with  the  effects  which  follow  from  unconscious 
selection,  that  is,  the  preservation  of  the  most  useful  or 
beautiful  animals,  with  no  intention  of  modifying  the 
breed;  but  by  this  process  of  unconscious  selection,  various 
breeds  have  been  sensibly  changed  in  the  course  of  two  or 
three  centuries. 

Species,  however,  probably  change  much  more  slowly, 
and  within  the  same  country  only  a  few  change  at  the  same 
time.  This  slowness  follows  from  all  the  inhabitants  of 
the  same  country  being  already  so  well  adapted  to  each 
other,  that  new  places  in  the  polity  of  nature  do  not  occur 
until  after  long  intervals,  due  to  the  occurrence  of  physical 
changes  of  some  kind,  or  through  the  immigration  of  new 
forms.  Moreover,  variations  or  individual  differences  of 
the  right  nature,  by  which  some  of  the  inhabitants  might 
be  better  fitted  to  their  new  places  under  the  altered 
circumstance,  would  not  always  occur  at  once.  Un¬ 
fortunately  we  have  no  means  of  determining,  according 
to  the  standard  of  years,  how  long  a  period  it  takes  to 
modify  a  species;  but  to  the  subject  of  time  we  must 
return. 

ON  THE  POORNESS  OP  PALAEONTOLOGICAL  COLLECTIONS. 

Now  let  us  turn  to  our  richest  geological  museums,  and 
what  a  paltry  display  we  behold!  That  our  collections  are 
imperfect  is  admitted  by  every  one.  The  remark  of  that 
admirable  palaeontologist,  Edward  Forbes,  should  never  be 
forgotten,  namely,  that  very  many  fossil  species  are  known 
and  named  from  single  and  often  broken  specimens,  or 
from  a  few  specimens  collected  on  some  one  spot.  Only 
a  small  portion  of  the  surface  of  the  earth  has  been 
geologically  explored,  and  no  part  with  sufficient  care,  as 
the  important  discoveries  made  every  year  in  Europe 
prove.  No  organism  wholly  soft  can  be  preserved.  Shells 
and  bones  decay  and  disappear  when  left  on  the  bottom  of 
the  sea,  where  sediment  is  not  accumulating.  We  prob¬ 
ably  take  a  quite  erroneous  view,  when  we  assume  that 
sediment  is  being  deposited  over  nearly  the  whole  bed  of 
the  sea,  at  a  rate  sufficiently  quick  to  imbed  and  preserve 
fossil  remains.  Throughout  an  enormously  large  propor¬ 
tion  of  the  ocean,  the  bright  blue  tint  of  the  water  be- 


320 


THE  POORNESS  OF 


speaks  its  purity.  The  many  cases  on  record  of  a  forma¬ 
tion  conformably  covered,  after  an  immense  interval  of 
time,  by  another  and  later  formation,  without  the  under¬ 
lying  bed  having  su  ffered  in  the  interval  any  wear  and  tear, 
seem  explicable  only  on  the  view  of  the  bottom  of  the  sea 
not  rarely  lying  for  ages  in  an  unaltered  condition. 
The  /emaitis  which  do  become  imbedded,  if  in  sand 
or  gravel,  will,  when  the  beds  are  upraised,  generally 
be  dissolved  by  the  percolation  of  rain  water  charged 
with  carbolic  acid.  Some  of  the  many  kinds  of  animals 
which  live  on  the  beach  between  high  and  low  water 
mark  seem  to  be  rarely  preserved.  For  instance,  the 
several  species  of  the  Clithamalinse  (a  sub-family  of  sessile 
cirripedes)  coat  the  rocks  all  over  the  world  in  infinite 
numbers  they  are  all  strictly  littoral,  with  the  exception  of 
a  single  Mediterranean  species,  which  inhabits  deep  water, 
and  this  has  been  found  fossil  in  Sicily,  whereas  not  one 
other  species  has  hitherto  been  found  in  any  tertiary  for¬ 
mation:  yet  it  is  known  that  the  genus  Chthamalus  existed 
during  the  Chalk  period.  Lastly,  many  great  deposits, 
requiring  a  vast  length  of  time  for  their  accumulation,  are 
entirely  destitute  of  organic  remains,  without  our  being 
able  to  assign  any  reason:  one  of  the  most  striking  in¬ 
stances  is  that  of  the  Flysch  formation,  which  consists  of 
shale  and  sandstone,  several  thousand,  occasionally  even 
six  thousand  feet  in  thickness,  and  extending  for  at  least 
300  miles  from  Vienna  to  Switzerland;  and  although  this 
great  mass  has  been  most  carefully  searched,  no  fossils, 
except  a  few  vegetable  remains,  have  been  found. 

With  respect  to  the  terrestrial  productions  which  lived 
during  the  Secondary  and  Palaeozoic  periods,  it  is  super¬ 
fluous  to  state  that  our  evidence  is  fragmentary  in  an 
extreme  degree.  For  instance,  untill  recently  not  a  land- 
shell  was  known  belonging  to  either  of  these  vast  periods, 
with  the  exception  of  one  species  discovered  by  Sir  C.  Lyell 
and  Dr.  Dawson  in  the  carboniferous  strata  of  North 
America;  but  now  land-shells  have  been  found  in  the  lias. 
In  regard  to  mammiferous  remains,  a  glance  at  the  histor¬ 
ical  table  published  in  Lyelbs  Manual  will  bring  home  the 
truth,  how  accidental  and  rare  is  their  preservation,  far 
better  than  pages  of  detail.  Nor  is  their  rarity  surprising, 
when  we  remember  how  large  a  proportion  of  the  bones  of 


PALEONTOLOGICAL  COLLECTIONS. 


321 


tertiary  mammals  have  been  discovered  either  in  caves  or  in 
lacustrine  deposits;  and  that  not  a  cave  or  true  lacustrine 
bed  is  known  belonging  to  the  age  of  our  secondary  or 
palaeozoic  formations. 

But  the  imperfection  in  the  geological  record  largely  re¬ 
sults  from  another  and  more  important  cause  than  an}r  of 
the  foregoing;  namely,  from  the  several  formations  being 
separated  from  each  other  bv  wide  intervals  of  time.  This 
doctrine  has  been  emphatically  admitted  by  many  geologists 
and  palaeontologists,  who,  like  E.  Forbes,  entirely  disbe¬ 
lieve  in  the  change  of  species.  When  we  see  the  forma¬ 
tions  tabulated  in  written  works,  or  when  we  follow  them 
in  nature,  it  is  difficult  to  avoid  believing  that  thev  are 
closely  consecutive.  But  we  know,  for  instance,  from  Sir 
B.  Murchison's  great  work  on  Russia,  what  wide  gaps  there 
are  in  that  country  between  the  superimposed  formations; 
so  it  is  in  North  America,  and  in  many  other  parts  of  the 
world.  The  most  skillful  geologist,  if  his  attention  had 
been  confined  exclusively  to  these  large  territories,  would 
never  have  suspected  that  during  the  periods  which  were 
blank  and  barren  in  his  own  country,  great  piles  of  sedi¬ 
ment,  charged  with  new  and  peculiar  forms  of  life,  had 
elsewhere  been  accumulated.  And  if,  in  every  separate 
territory,  hardly  any  idea  can  be  formed  of  the  length  of 
time  which  has  elapsed  between  the  consecutive  forma¬ 
tions,  we  may  infer  that  this  could  nowhere  be  ascertained. 
The  frequent  and  great  changes  in  the  mineralogical  com¬ 
position  of  consecutive  formations,  generally  implying 
great  changes  in  the  geography  of  the  surrounding  lands, 
whence  the  sediment  was  derived,  accord  with  the  belief  of 
vast  intervals  of  time  having  elapsed  between  each  for¬ 
mation. 

We  can,  I  think,  see  why  the  geological  formations 
of  each  region  are  almost  invariable  intermittent;  that  is, 
have  not  followed  each  other  in  close  sequence.  Scarcely 
any  fact  struck  me  more  when  examining  many  hundred 
miles  of  the  South  American  coasts,  which  have  been  up¬ 
raised  several  hundred  feet  within  the  recent  period,  than 
the  absence  of  any  recent  deposits  sufficiently  extensive  to 
last  for  even  a  short  geological  period.  Along  the  whole 
west  coast,  which  is  inhabited  by  a  peculiar  marine  fauna, 
tertiary  beds  are  so  poorly  developed  that  no  record  of  sev- 


THE  POORNESS  OF 


322 

eral  successive  and  peculiar  marine  faunas  will  probably  ba 
preserved  to  a  distant  age.  A  little  reflection,  will  explain 
why,  along  the  rising  coast  of  the  western  side  of  South 
America,  no  extensive  formations  with  recent  or  tertiary 
remains  can  anywhere  be  found,  though  the  supply  of  sedi¬ 
ment  must  for  ages  have  been  great,  from  the  enormous 
degradation  of  the  coast  rocks  and  from  the  muddy  streams 
entering  the  sea.  The  explanation,  no. doubt,  is  that  the 
littoral  and  sublittoral  deposits  are  continually  worn  away, 
as  soon  as  they  are  brought  up  by.  the  slow  and  gradual 
rising  of  the  land  within  the  grinding  action  of  the  coast 

waves.  (  ,  , 

We  may,  I  think,  conclude  that  sediment  must  be  ac¬ 
cumulated  in  extremely  thick,  solid,  or  extensive  masses, 
in  order  to  withstand  the  incessant  action  of  the. waves, 
when  first  upraised  and  during  successive  oscillations  of 
level,  as  well  as  the  subsequent  subaerial  degradation. 
Such  thick  and  extensive  accumulations  of  sediment  may 
be  formed  in  two  wavs;  either  in  profound  depths  of  the 
sea,  in  which  case  the  bottom  will,  not  be  inhabited  by  so 
many  and  such  varied  forms  of  life,  as  the  more  shallow 
seas;  and  the  mass  when  upraised  will,  give  an.  imperfect 
record  of  the  organisms  which  existed  in  the  neighborhood 
during  the  period  of  its  accumulation.  Or  sediment  may 
be  deposited  to  any  thickness  and.  extent  over  a  shallow 
bottom,  if  it  continue  slowly  to  subside.  In  this  latter  case, 
as  long  as  the  rate  of  subsidence  and  the  supply  of  sedi¬ 
ment  nearly  balance  each  other,  the  sea  will  remain  shallow 
and  favorable  for  many  and  varied  forms,  and  thus  a  rich 
fossilifercus  formation,  thick  enough,  when  upraised,  to 
resist  a  large  amount  of  denudation,  may  be  formed.  . 

I  am  convinced  that  nearly  all  our  ancient  formations, 
which  are  throughout  the  greater  part  of  their  thickness 
rich  in  fossils,  have  thus  been  formed  during  subsidence. 
Since  publishing  my  views  on  this  subject  in  1845,  I  have 
watched  the  progress  of  geology,  and  have  been  surprised 
to  note  how  author  after  author,  in  treating  of  this  or  that 
great  formation,  has  come  to  the  conclusion  that  it  was 
accumulated  during  subsidence.  I  may  add,  that  the  only 
ancient  tertiary  formation  on  .the  west  coast  of  South 
America,  which  has  been  bulky  enough  to  resist  such  de¬ 
gradation  as  it  has  as  yet  suffered,  but  which  will  hardly 


PALEONTOLOGICAL  COLLECTIONS.  323 

last  to  a  distant  geological  age,  was  deposited  during  a 
downward  oscillation  of  level,  and  thus  gained  considerable 
thickness. 

All  geological  facts  tell  us  plainly  that  each  area  has 
undergone  numerous  slow  oscillations  of  level,  and  appar- 
ently  these  oscillations  have  affected  wide  spaces.  Conse¬ 
quently,  formations  rich  in  fossils  and  sufficiently  thick 
and  extensive  to  resist  subsequent  degradation,  will  have 
been  formed  over  wide  spaces  during  periods  of  sub¬ 
sidence,  but  only  where  the  supply  of  sediment  was 
sufficient  to  keep  the  sea  shallow  and  to  embed  and 
preserve  the  remains  before  they  had  time  to  decay.  On 
the  other  hand,  as  long  as  the  bed  of  the  sea  remains  sta¬ 
tionary,  thick  deposits  cannot  have  been  accumulated  in 
the  shallow  parts,,  which  are  the  most  favorable  to  life. 
Still  less  can  this  have  happened  during  the  alternate 
periods  of -elevation;  or,  to  speak  more  accurately,  the  beds 
which  were  then  accumulated  will  generally  have  been  de¬ 
stroyed  by  being  upraised  and  brought  within  the  limits  of 
the  coast-action. 

These  remarks  apply  chiefly  to  littoral  and  sublittoral 
depositsc  In  the  case  of  an  extensive  and  shallow  sea,  such 
as  that  within  a  large  part  of  the  Malay  Archipelago, 
where  the  depth  varies  from  thirty  or  forty  to  sixty  fath¬ 
oms,  a  widely  extended  formation  might  be  formed  during 
a  period  of  elevation,  and  yet  not  suffer  excessively  from 
denudation  during  its  slow  upheaval;  but  the  thickness 
of  the  formation  could  not  be  great,  for  owing  to  the  ele- 
vatory  movement  it  would  be  less  than  the  depth  in  which 
it  was  formed;  nor  would  the  deposit  be  much  consoli¬ 
dated,  nor  be  capped  by  overlying  formations,  so  that  it 
would  run  a  good  chance  of  being  worn  away  by  atmos¬ 
pheric  degradation  and  by  the  action  of  the  sea  during 
subsequent  oscillations  of  level.  It  has,  however,  been 
suggested  by  Mr.  Hopkins,  that  if  one  part  of  the  area, 
after  rising  and  before  being  denuded,  subsided,  the 
deposit  formed  during  the  rising  movement,  though  not 
thick,  might  afterward  become  protected  by  fresh  accumu¬ 
lations,  and  thus  be  preserved  for  a  long  period. 

Mr„  Hopkins  also  expresses  his  belief  that  sedimentary 
beds  of  considerable  horizontal  extent  have  rarely  been 
completely  destroyed.  But  all  geologists,  excepting  the 


TUE  POORNESS  OF 


t 


324 


few  who  believe  that  our  present  metamorphic  schists  and 
plutonic  rocks  once  formed  the  primordial  nucleus  of  the 
globe,  will  admit  that  these  latter  rocks  have  been  stripped 
of  their  covering  to  an  enormous  extent.  For  it  is 
scarcelv  possible  that  such  rocks  could  have  been  solidified 
and  crystallized  while  uncovered;  but  if  the  metamorphic 
faction,  occurred  at  profound  depths  of  the  ocean,  the 
former  protecting  mantle  of  rock  may  not  have  been  very 
thick.  Admitting  then  that  gneiss,  mica-schist,  granite, 
diorite,  etc.,  were  once  necessarially  covered  up,  how  can 
we  account  for  the  naked  and  extensive  areas  of  such  rocks 
in  many  parts  of  the  world,  except  on  the  belief  that  they 
have  subsequently  been  completely  denuded  of  all  over¬ 
ling  strata?  That  such  extensive  areas  do  exist  cannot 
be  doubted';  the  granitic  region  of  Parime  is  described 
by  Humboldt  as  being  at  least  nineteen  times  as  large 
as  Switzerland,  South  of  the  Amazon,  Bone  colors 
an  area  composed  of  rocks  of  this  nature  as  equal  to  that 
of  Spain,  France*  Italy,  part  of  Germany,  and  the  British 
Islands,  all  conjoined.  This  region  has  not  been  carefully 
explored,  but  from  the  concurrent  testimony  of  travelers, 
the  granitic  area  is  very  large:  thus  Yon  Eschwege  gives  a 
detailed  section  of  these  rocks,  >  stretching  from  Rio  de 
Janeiro  for  260  geographical  miles  inland  in  a  straight 
line;  and  I  traveled  for  150  miles  in  another  direction,  and 
saw"  nothing  but  granitic  rocks.  Numerous  specimens, 
collected  along  the  whole  coast,  from  near  Rio  Janeiro  to 
the  mouth  of  the  Plata,  a  distance  of  1,100  geographical 
miles,  were  examined  by  me,  and  they  all  belonged  to 
this  class.  Inland,  along  the  whole  northern  bank  of 
the  Plata,  I  saw,  besides  modern  tertiary  beds,  only  one 
small  patch  of  slightly  metamorphosed  rock,  which  alone 
could  have  formed  a  part  of  the  original  capping  of  the 
granitic  series.  Turning  to  a  well-known  region,  namely, 
to  the  United  States  and  Canada,  as  shown  in  Professor  H. 
D.  Rogers’  beautiful  map,  I  have  estimated  the  areas  by 
cutting  out  and  weighing  the  paper,  and  I  find  that  the 
metamorphic  (excluding  the  “  semi-metamorphic  ”)  and 
granite  rocks  exceed,  in  the  proportion  of  19  to  12.5, 
the  whole  of  the  newer  Paleozoic  formations.  In  many 
regions  the  metamorphic  and  granite  rocks  would  be  found 
much  more  widely  extended  than  they  appear  to  be,  if  all 


PALEONTOLOGICAL  COLLECTIONS.  325 

the  sedimentary  beds  were  removed  which  rest  uncon- 
formably  on  them,  and  which  could  not  have  formed  part 
of  the  original  mantle  under  which  they  were  crystallized. 
Hence,  it  is  probable  that  in  some  parts  of  the  world  whole 

formations  have  been  completely  denuded,  with  not  a  wreck 
leit  behind. 

One  remark  is  here  worth  a  passing  notice.  During 
periods  of  elevation  the  area  of  the  land  and  of  the  adioin- 
lng  shoal  parts  of  the  sea  will  be  increased  and  new  sta¬ 
tions  will  often  be  formed— all  circumstances  favorable,  as 
P**®^*^  ,y  explained,  for  the  formation  of  new  varieties 
and  species;  but  during  such  periods  there  will  generally 
be  a  blank  m  the  geological  record.  On  the  other  hand, 
during  subsidence,  the  inhabited  area  and  number  of 
inhabitants  will  decrease  (excepting  on  the  shores  of  a 
continent  when  first  broken  up  into  an  archipelago),  and 
consequently  during  subsidence,  though  there  will  be 
much  extinction,  few  new  varieties  or  species  will  be 
formed;  and  it  is  during  these  very  periods  of  subsidence 
that  the  deposits  which  are  richest  in  fossils  have  been 
accumulated. 

OH"  THE  ABSENCE  OF  NUMEROUS  INTERMEDIATE  VARIE¬ 
TIES  IN  ANY  SINGLE  FORMATION. 

From  these  several  considerations  it  cannot  be  doubted 
that  the  geological  record,  viewed  as  a  whole,  is  extremely 
imperfect;  but  if  we  confine  our  attention  to  any  one 
formation,  it  becomes  much  more  difficult  to  understand 
why  we  do  not  therein  find  closely  graduated  varieties 
between  the  allied  species  which  lived  at  its  commence¬ 
ment  and.  at  its  close.  Several  cases  are  on  record  of  the 
same  species  presenting  varieties  in  the  upper  and  lower 
parts  of  the  same  formation.  Thus  Trautschold  gives  a 
number  of  instances  with  Ammonites,  and  Hilgendorf  has 
described  a  most  curious  case  of  ten  graduated  forms  of 
rlanorbis  multiformis  in  the  successive  beds  of  a  fresh¬ 
water  formation  in  Switzerland.  Although  each  formation 
has  indisputably  required  a  vast  number  of  years  for  its 
deposition,  several  reasons  can  be  given  why  each  should 
not  commonly  include  a  graduated  series  of  links  between 
the  species  which  lived  at  its  commencement  and  close,  but 


326  ABSENCE  OF  INTERMEDIATE  VARIETIES 


I  cannot  assign  due  proportional  weight  to  the  following 
considerations. 

Although  each  formation  may  mark  a  very  long  lapse  of 
years,  each  probably  is  short  compared  with  the  period 
requisite  to  change  one  species  into  another.  I  am  aware 
that  two  palaeontologists,  whose  opinions  are  worthy  of 
much  deference,  namely  Bronn  and  Woodward,  have  con¬ 
cluded  that  the  average  duration  of  each  formation  is  twice 
or  thrice  as  long  as  the  average  duration  of  specific  forms. 
But  insuperable  difficulties,  as  it  seems  to  me,  prevent  us 
from  coming  to  any  just  conclusion  on  this  head.  When 
we  see  a  species  first  appearing  in  the  middle  of  any  forma¬ 
tion,  it  would  be  rash  in  the  extreme  to  infer  that  it  had 
not  elsewhere  previously  existed.  So  again,  when  we  find 
a  species  disappearing  before  the  last  layers  have  been  de¬ 
posited,  it  would  be  equally  rash  to  suppose  that  it  then 
became  extinct.  We  forget  how  small  the  area  of  Europe 
is  compared  with  the  rest  of  the  world;  nor  have  the  sev¬ 
eral  stages  of  the  same  formation  throughout  Europe  been 
correlated  with  perfect  accuracy. 

We  may  safely  infer  that  with  marine  animals  of  all 
kinds  there  has  been  a  large  amount  of  migration  due  to 
climatal  and  other  changes;  and  when  we  see  a  species  first 
appearing  in  any  formation,  the  probability  is  that  it  only 
then  first  immigrated  into  that  area.  It  is  well-known, 
for  instance,  that  several  species  appear  somewhat  earlier 
in  the  palaeozoic  beds  of  North  America  than  in  those  of 
Europe;  time  having  apparently  been  required  for  their 
migration  from  the  American  to  the  European  seas.  In 
examining  the  latest  deposits,  in  various  quarters  of  the 
world,  it  has  everywhere  been  noted,  that  some  few  still 
existing  species  are  common  in  the  deposit,  but  have 
become  extinct  in  the  immediately  surrounding  sea;  or, 
conversely,  that  some  are  now  abundant  in  the  neighbor¬ 
ing  sea,  but  are  rare  or  absent  in  this  particular  deposit. 
It  is  an  excellent  lesson  to  reflect  on  the  ascertained 
amount  of  migration  of  the  inhabitants  of  Europe  during 
the  glacial  epoch,  which  forms  only  a  part  of  one  whole 
geological  period;  and  likewise  to  reflect  on  the  changes 
of  level,  on  the  extreme  change  of  climate,  and  on  the 
great  lapse  of  time,  all  included  within  this  same  glacial 
period.  Yet  it  may  be  doubted  whether,  in  any  quarter  of 


IN  ANT  SINGLE  FORMATION.  33? 

the  world,  sedimentary  deposits,  including  fossil  remains, , 
have  gone  on  accumulating  within  the  same  area  during 
the  whole  of  this  period.  It  is  not,  for  instance,  probable 
that,  sediment  was  deposited  during  the  whole  of  the 
glacial  period  near  the  mouth  of  the  Mississippi,  within 
that  limit  of  depth  at  which  marine  animals  can  best 
flouiish.  for  we  know  that  great  geographical  changes 
occurred  in  other  parts  of  America  during  this  space  of 
time.  When  such  beds  as  were  deposited  in  shallow  water 
near  the  mouth  of  the  Mississippi  during  some  part  of  the 
glacial  period  shall  have  been  upraised,  organic  remains 
will  probably  first  appear  and  disappear  at  different  levels, 
owing  to  the  migrations  of  species  and  to  geographical 
changes.  And  in  the  distant  future,  a  geologist,  examin¬ 
ing  these  beds,  would  be  tempted  to  conclude  that  the 
average  duration  of  life  of  the  embedded  fossils  had  been 
less  than  that  of  the  glacial  period,  instead  of  having  been 
really  far  greater,  that  is,  extending  from  before  the  glacial 
epoch  to  the  present  day. 

.  **  order  to  get  a  perfect  gradation  between  two  forms 
in  tne  upper  and  lower  parts  of  the  same  formation,  the 
deposit  must  have  gone  on  continuously  accumulating 
dining  a. long  period,  sufficient  for  the  slow  process  of 
modification;  hence,  the  deposit  must  be  a  very  thick 
one;  and  the  species  undergoing  change  must  have  lived 
m  the  same  district  throughout  the  whole  time,,  But 
we  have  seen  that  a  thick  formation,  fossiliferous 
throughout  its  entire  thickness,  can  accumulate  only 
during,  a  period  of  subsidence;  and  to  keep  the  depth 
approximately  the  same,  which  is  necessary  that  the 
same  marine  species  may  live  on  the  same  space,  the  sun- 
ply  of  sediment  must  nearly  counterbalance  the  amount 
of  subsidence.  But  this  same  movement  of  subsi¬ 
dence,  will  tend  to  submerge  the  area  whence  the  sediment 
is  derived,  and  thus  diminish  the  supply,  while  the  down¬ 
ward  movement  continues0  In  fact,  this  nearly  exact  bal¬ 
ancing  between  the  supply  of  sediment  and  the  amount  of 
subsidence  is  probably  a  rare  contingency;  for  it  has  been 
observed  by  more  than  one  palasontologist  that  very  thick 
deposits  are  usually  barren  of  organic  remains,  except  near 
their  upper  or  lower  limits. 

It  would  seem  that  each  separate  formation,  like  the 


328  ABSENCE  OF  INTERMEDIATE  VARIETIES 


whole  pile  of  formation  in  any  country,  has  generally  been 
intermittent  in  its  accumulation.  When  we  see,  as  is  so 
often  the  case,  a  formations  composed  of  beds  of  widely 
different  mineralogical  composition,  we  may  reasonably 
suspect  that  the  process  of  deposition  has  been  more  or  less 
interrupted.  Nor  will  the  closest  inspection  of  a  forma¬ 
tion  give  us  any  idea  of  the  length  of  time  which  its  depo¬ 
sition  may  have  consumed^  Many  instances  could  be 
given  of  beds,  only  a  few  feet  in  thickness,  representing 
formations  which  are  elsewhere  thousands  of  feet  in  thick¬ 
ness,  and  which  must  have  required  an  enormous  period 
for  their  accumulation;  yet  no  one  ignorant  of  this  fact 
would  have  even  suspected  the  vast  lapse  of  time  repre¬ 
sented  by  the  thinner  formation0  Many  cases  could  be 
given  of  the  lower  beds  of  a  formation  having  been  up¬ 
raised,  denuded,  submerged,  and  then  recovered  by  the 
upper  beds  of  the  same  formation — facts,  showing  what 
wide,  yet  easily  overlooked,  intervals  have  occurred  in  its 
accumulation.  In  other  cases  we  have  the  plainest  evi¬ 
dence  in  great  fossilized  trees,  still  standing  upright  as 
they  grew,  of  many  long  intervals  of  time  and  changes  of 
level  during  the  process  of  deposition,  which  would  not 
have  been  suspected,  had  not  the  trees  been  preserved:  thus 
Sir  Co  Lyell  and  Dr„  Dawson  found  carboniferous  beds 
1,400  feet  thick  in  Nova  Scotia,  with  ancient  root-bearing 
strata,  one  above  the  other,  at  no  less  than  sixty-eiglit  dif¬ 
ferent  levels.  Hence,  when  the  same  species  occurs  at  the 
bottom,  middle,  and  top  of  a  formation,  the  probability  is 
that  it  has  not  lived  on  the  same  spot  during  the  whole 
period  of  deposition,  but  has  disappeared  and  reappeared, 
perhaps  many  times,  during  the  same  geological  period. 
Consequently  if  it  were  to  undergo  a  considerable  amount 
of  modification  during  the  deposition  of  any  one  geological 
formation,  a  section  would  not  include  all  the  fine  inter¬ 
mediate  gradations  which  must  on  our  theory  have  existed, 
but  abrupt,  though  perhaj^s  slight,  changes  of  form. 

It  is  all-important  to  remember  that  naturalists  have  no 
go'den  rule  by  which  to  distinguish  species  and  varieties; 
they  grant  some  little  variability  to  each  species,  but  when 
they  meet  with  a  somewhat  greater  amount  of  difference 
between  any  two  forms,  they  rank  botli  as  species,  unless 
they  are  enabled  to  connect  them  together  by  the  closest 


IN  ANY  SINGLE  FORMATION.  330 

intermediate  gradations;  and  this,  from  the  reasons  just 
assigned,  we  can  seldom  hope  to  effect  in  any  one  geolog- 

2K  “YT  i  S!?PP0!mg  B  and  c  to  be  two  species,  and^a 
t  ilia.  A,  to  be  found  m  an  older  and  underlying  bed*  even 
if  A  were  strictly  intermediate  between  B  and  C,  it  would 
simply  be  ranked  as  a  third  and  distinct  species,  unless  at 
the  same  time  it  could  be  closely  connected  by  intermedi¬ 
ate  varieties  with  either  one  or  both  forms.  Nor  should  it 
be  forgotten,  as  before  explained,  that  A  might  be  the 

he  P  °|B.  a?d  C>  and  ?efc  would  not  necessarily 

be  stnctly  intermediate  between  them  in  all  respects.  So 

that  we  might  obtain  the  parent-species  and  its  several 
modified  descendants  from  the  lower  and  upper  beds  of  the 
same  formation,  and  unless  we  obtained  numerous  transi¬ 
tional  gradations,  we  should  not  recognize  their  blood-rela- 

tionship,  and  should  consequently  rank  them  as  distinct 
species. 

It  is  notorious  on  what  excessively  slight  differences 
many  paleontologists  have  founded  their  species;  and  they 
do  tins  the  more  readily  if  the  specimens  come  from  differ¬ 
ent  sub-stages  of  the  same  formation.  Some  experienced 
conchologists  are  now  sinking  many  of  the  very  fine  species  of 
7?  yrh}gl'y  and  others  into  the  rank  of  varieties;  and  on 
this  view  we  do  find  the  kind  of  evidence  of  change  which 
on  the  theory  we  ought  to  find.  Look  again  at  the  later 
tertiary  deposits,  which  include  many  shells  believed  by 
the  majority  of  naturalists  to  be  identical  with  existing 
species;  but  some  excellent  naturalists,  as  Agassiz  and 
Pictet,  maintain  that  all  these  tertiary  species  are  specific¬ 
ally  distinct,  though  the  distinction  is  admitted  to  be  very 
slight;  so  that  here,  unless  we  believe  that  these  eminent 
naturahsts  have  been  misled  by  their  imaginations,  and 
that  these  late  tertiary  species  really  present  no  difference 
whatever  from  their  living,  representatives,  or  unless  we 

111  °PP?.slfclon  to  the  judgment  of  most  naturalists, 
that  these  tertiary  species  are  all  truly  distinct  from  the 
recent,  we  have  evidence  of  the  frequent  occurrence  of  slight 
modifications  of  the  kind  required.  If  we  look  to  rather 
wider  intervals  of  time,  namely,  to  distinct  but  consecu- 

Saa#aS  f  ?reat  formation,  we  find  that  the 

embeddeii  fossils  though  universally  ranked  as  specific¬ 
ally  different,  yet  are  far  more  closely  related  to  each  other 


330  ABSENCE  OF  INTERMEDIATE  VARIETIES 

than  are  the  species  found  in  more  widely  separated  foima- 
tions;  so  that  here  again  we  have  undoubted  evidence  of 
change  in  the  direction  required  by  the  theoiy ;  but  to  this 
latter  subject  I  shall  return  in  the  following  chapter. 

With  animals  and  plants  that  propagate  rapidly  and  do 
not  wander  much,  there  is  reason  to  suspect,  as  we 
have  formerly  seen,  that  their  varieties  are  geneially  at 
first  local;  and  that  such  local  varieties  do  not  spread 
widely  and  supplant  their  parent-form  until  they  have 
been  modified  and  perfected  in  some  considerable  degree. 
According  to  this  view,  the  chance  of  discovering  in  a 
formation  in  any  one  country  all  the  early  stages  of  tiansn 
tion  between  any  two  forms,  is  small,  for  the  successive 
changes  are  supposed  to  have  been  local  or  confined  to 
some  one  spot.  Most  marine  animals  have  a  wide  lange, 
and  we  have  seen  that  with  plants  it  is  those  which  have 
the  widest  range,  that  oftenest  present  varieties;  so  that, 
with  shells  and  other  marine  animals,  it  is  probable  that 
those  which  had  the  widest  range,  far  exceeding  the  limits 
of  the  known  geological  formations  in  Europe,  have  often¬ 
est  given  rise,  first  to  local  varieties  and  ultimately  to  new 
species;  and  this  again  would  greatly  lessen  the  chance  of 
our  being  able  to  trace  the  stages  of  transition  in  any  one 
geological  formation. 

It  is  a  more  important  consideration,  leading  to  the  same 
result,  as  lately  insisted  on  by  Dr.  Falconer,  namely,  that 
the  period  during  which  each  species  underwent  modifica¬ 
tion,  though  long  as  measured  by  years,  was  probably  short 
in  comparison  with  that  during  which  it  remained  without 
undergoing  any  change. 

It  should  not  be  forgotten,  that  at  the  present  day,  with 
perfect  specimens  for  examination,  two  forms  can 
seldom  be  connected  by  intermediate  varieties,  and  thus 
proved  to  be  the  same  species,  until  many  specimens  are 
collected  from  many  places;  and  with  fossil  species  this 
can  rarelv  be  done.  We  shall,  perhaps,  best  perceive  the 
improbability  of  our  being  enabled  to  connect  species  by 
numerous,  fine,  intermediate,  fossil  links,  by  asking  0111- 
selves  whether,  for  instance,  geologists  at  some  futuie 
period  will  be  able  to  prove  that  our  different  breeds  of 
cattle,  sheep,  horses,  and  dogs  are  descended  from  a  single 
stock  or  from  several  aboriginal  stocks;  or  again,  whether 


IN  ANT  SINGLE  FORMA  I  ION.  33l 

certain  sea-shells  inhabiting  the  shores  of  North  America, 
which  are  ranked  by  some  conchologists  as  distinct  species 
from  their  European  representatives,  and  by  other  con¬ 
chologists  as  only  varieties,  are  really  varieties,  or  are,  as 
it  is  called,  specifically  distinct.  This  could  be  effected 
by  the  future  geologist  only  by  his  discovering  in  a  fossil 
state  numerous  intermediate  gradations;  and  such  success 
is  improbable  in  the  highest  degree. 

It  has  been  asserted  over  and  over  again,  by  writers  who 
believe  in  the  immutability  of  species,  that  geology  yields 
no  linking  forms.  This  assertion,  as  we  shall  see  in  the 
next  chapter,  is  certainly  erroneous.  As  Sir  J.  Lubbock 
has  remarked,  “  Every  species  is  a  link  between  other  allied 
forms. ”  If  we  take  a  genus  having  a  score  of  species, 
recent  and  extinct,  and  destroy  four-fifths  of  them,  no  one 
doubts  that  the  remainder  will  stand  much  more  distinct 
from  each  other.  If  the  extreme  forms  in  the  genus 
happen  to  have  been  thus  destroyed,  the  genus  itself  will 
stand  more  distinct  from  other  allied  genera.  What  geo¬ 
logical  research  has  not  revealed,  is  the  former  existence  of 
ififinitely  numerous  gradations,  as  fine  as  existing  varieties, 
connecting  together  nearly  all  existing  and  extinct  species. 
But  this  ought  not  to  be  expected ;  yet  this  has  been 
repeatedly  advanced  as  a  most  serious  objection  against 
my  views. 

It  may  be  worth  while  to  sum  up  the  foregoing  remarks 
on  the  causes  of  the  imperfection  of  the  geological  record 
under  an  imaginary  illustration.  The  Malay  Archipelago 
is  about  the  size  of  Europe  from  the  North  Cape  to  the 
Mediterranean,  and  from  Britain  to  Bussia  ;  and  therefore 
equals  all  the  geological  formations  which  have  been 
examined  with  any  accuracy,  excepting  those  of  the  United 
States  of  America.  I  fully  agree  with  Mr.  God  win- Austen, 
that  the  present  condition  of  the  Malay  Archipelago,  with 
its  numerous  large  islands  separated  by  wide  and  shallow 
seas,  probably  represents  the  former  state  of  Europe, 
while  most  of  our  formations  were  accumulating.  The 
;  Malay  Archipelago  is  one  of  the  richest  regions  in  organic 
beings ;  yet.  if  all  the  species  were  to  be  collected  which 
have  ever  lived  there,  how  imperfectly  would  they  repre¬ 
sent  the  natural  history  of  the  world  ! 

But  we  have  every  reason  to  believe  that  the  terrestrial 


3 32  ABSENCE  OF  INTERMEDIATE  VARIETIES 


productions  of  the  archipelago  would  be  preserved  in  an 
extremely  imperfect  manner  in  the  formations  which  we 
suppose  to  be  there  accumulating.  Not  many  of  the 
strictly  littoral  animals,  or  of  those  which  lived  on  naked 
submarine  rocks,  would  be  embedded;  and  those  embedded 
in  gravel  or  sand  would  not  endure  to  a  distant  epoch. 
Wherever  sediment  did  not  accumulate  on  the  bed  of  the 
sea,  or  where  it  did  not  accumulate  at  a  sufficient  rate  to 
protect  organic  bodies  from  decay,  no  remains  could  be 
preserved. 

Formations  rich  in  fossils  of  many  kinds,  and  of  thick¬ 
ness  sufficient  to  last  to  an  age  as  distant  in  futurity  as  the 
secondary  formations  lie  in  the  past,  would  generally  be 
formed  in  the  archipelago  only  during  periods  of  subsi¬ 
dence.  These  periods  of  subsidence  would  be  separated 
from  each  other  by  immense  intervals  of  time,  during 
which  the  area  would  be  either  stationary  or  rising;  while 
rising,  the  fossiliferous  formations  on  the  steeper  shores 
would  be  destroyed,  almost  as  soon  as  accumulated,  by  the 
incessant  coast-action,  as  we  now  see  on  the  shores  of  South 
America.  Even  throughout  the  extensive  and  shallow 
seas  within  the  archipelago,  sedimentary  beds  could  hardly 
be  accumulated  of  great  thickness  during  the  periods  of 
elevation,  or  become  capped  and  protected  by  subsequent 
deposits,  so  as  to  have  a  good  chance  of  enduring  to  a  very 
distant  future.  During  the  periods  of  subsidence,  there 
would  probably  be  much  extinction  of  life;  during  the 
periods  of  elevation,  there  would  be  much  variation,  but 
the  geological  record  would  then  be  less  perfect. 

It  may  be  doubted  whether  the  duration  of  any  one  great 
period  of  subsidence  over  the  whole  or  part  of  the  archi¬ 
pelago,  together  with  a  contemporaneous  accumulation  of 
sediment,  would  exceed  the  average  duration  of  the  same 
specific  forms;  and  these  contingencies  are  indispensable 
for  the  preservation  of  all  the  transitional  gradations  be¬ 
tween  any  two  or  more  species.  If  such  gradations  were 
not  all  fully  preserved,  transitional  varieties  would  merely 
appear  as  so  many  new,  though  closely  allied  species.  It 
is  also  probable  that  each  great  period  of  subsidence  would 
be  interrupted  by  oscillations  of  level,  and  that  slight  cli- 
matical  changes  would  intervene  during  such  lengthy 
periods;  and  in  these  cases  the  inhabitants  of  the  arch;- 


IN  ANY  SINGLE  FORMATION . 


833 


pelago  would  migrate,  and  no  closely  consecutive  record  of 
their  modifications  could  be  preserved  in  any  one  forma¬ 
tion. 

Very  many  of  the  marine  inhabitants  of  the  archipelago 
now  range  thousands  of  miles  beyond  its  confines;  and 
analogy  plainly  leads  to  the  belief  that  it  would  be  chiefly 
these  far-ranging  species,  though  only  some  of  them, 
which  would  oftenest  produce  new  varieties;  and  the  vari¬ 
eties  would  at  first  be  local  or  confined  to  one  place,  but  if 
possessed  of  airy  decided  advantage,  or  when  further  modi¬ 
fied.  and  improved,  they  would  slowly  spread  and  supplant 
their  parent-forms.  When  such  varieties  returned  to  their 
ancient  homes,  as  they  would  differ  from  their  former  state 
in  a  nearly  uniform,  though  perhaps  extremely  slight  degree, 
and  as  they  would  be  found  imbedded  in  slightly  differ¬ 
ent  sub-stages  of  the  same  formation,  they  would,  accord¬ 
ing  to  the  principles  followed  by  many  paleontologists,  be 
ranked  as  new  and  distinct  species. 

If  then  there  be  some  degree  of  truth  in  these  remarks, 
we  have  no  right  to  expect  to  find,  in  our  geological  for¬ 
mations,  an  infinite  number  of  those  fine  transitional  forms 
which,  on  our  theory,  have  connected  all  the  past  and 
present  species  of  the  same  group  into  one  long  and  branch¬ 
ing  chain  of  life.  We  ought  only  to  look  for  a  few  links, 
and  such  assuredly  we  do  find — some  more  distantlv,  some 
more  closely,  related  to  each  other;  and  these  links,  let 
them  be  ever  so  close,  if  found  in  different  stages  of  the 
same  formation,  would,  by  many  palaeontologists,  be 
ranked  as  distinct  species.  But  I  do  not  pretend  that  I 
should  ever  have  suspected  how  poor  was  the  record  in  the 
best  preserved  geological  sections,  had  not  the  absence  of 
innumerable  transitional  links  between  the  species  which 
lived  at  the  commencement  and  close  of  each  formation, 
pressed  so  hardly  on  my  theory. 

ON  THE  SUDDEN  APPEARANCE  OF  WHOLE  GROUPS  OF 

ALLIED  SPECIES. 

The  abrupt  manner  in  which  whole  groups  of  species 
suddenly  appear  in  certain  formations,  has  been  urged  by 
several  palaeontologists— for  instance,  by  Agassiz,  Pictet, 
and  Sedgwick — as  a  fatal  objection  to  the  belief  in  the 


SUDDEN  APPEARANCE  OF 


334 

transmutation  of  species.  If  numerous  species,  belonging 
to  the  same  genera  or  families,  have  really  started  into  life 
at  once,  the  fact  would  be  fatal  to  the  theory  of  evolution 
through  natural  selection.  For  the  development  by  this 
means  of  a  group  of  forms,  all  of  which  are  descended  from 
some  one  progenitor,  must  have  been  an  extremely  slow 
process;  and  the  progenitors  must  have  lived  long  before 
their  modified  descendants.  But  we  continually  overrate 
the  perfection  of  the  geological  record,  and  falsely  infer, 
because  certain  genera  or  families  have  not  been  found  be¬ 
neath  a  certain  stage,  that  they  did  not  exist  before  that 
stage.  In  all  cases  positive  palaeontological  evidence  may 
be  implicitly  trusted;  negative  evidence  is  worthless,  as 
experience  has  so  often  shown.  We  continually  forget  how 
large  the  world  is,  compared  with  the  area  over  which  our 
geological  formations  have  been  carefully  examined;  we 
forget  that  groups  of  species  may  elsewhere  have  long 
existed,  and  have  slowly  multiplied,  before  they  invaded 
the  ancient  archipelagoes  of  Europe  and  the  Unites  States. 
We  do  not  make  due  allowance  for  the  intervals  of  time 
which  have  elapsed  between  our  consecutive  formations, 
longer  perhaps  in  many  cases  than  the  time  requiied  foi 
the  accumulation  of  each  formation.  These  intervals  will 
have  given  time  for  the  multiplication  of  species  from  some 
one  parent-form:  and  in  the  succeeding  formation,  such 
groups  or  species  will  appear  as  if  suddenly  created. 

I  may  here  recall  a  remark  formerly  made,  namely,  that 
it  might  require  a  long  succession  of  ages  to  adapt  an  or¬ 
ganism  to  some  new  and  peculiar  line  of  life,  for  instance, 
to  fly  through  the  air;  and  consequently  that  the  transi¬ 
tional  forms  would  often  long  remain  confined  to  some  one 
region;  but  that,  when  this  adaptation  had  once  been 
effected,  and  a  few  species  had  thus  acquired  a  great  ad¬ 
vantage  over  other  organisms,  a  comparatively  short  time 
would  be  necessary  to  produce  many  divergent  forms, 
which  would  spread  rapidly  and  widely  throughout  the 
world.  Professor  Pictet,  in  his  excellent  Review  of  this 
work,  in  commenting  on  early  transitional  forms,  and 
taking  birds  as  an  illustration,  cannot  see  how  the  succes¬ 
sive  modifications  of  the  anterior  limhs  of  a  supposed  pro¬ 
totype  could  possibly  have  been  of  any  advantage.  But 
look  at  the  penguins  of  the  Southern  Ocean;  have  not 


GEO  UPS  OF  ALLIED  SPECIES .  335 

these  birds  their  front  limbs  in  tliis  precise  intermediate 
state  of  “ neither  true  arms  nor  true  wings?”  Yet  these 
birds  hold  their  place  victoriously  in  the  battle  for  life;  for 
they  exist  in  infinite  numbers  and  of  many  kinds.  I  do 
not  suppose,  that  we  here  see  the  real  transitional  grades 
through  which  the  wings,  of  birds  have  passed;  but  what 
special  difficulty  is  there  in  believing  that  it  might  profit 
the  modified  descendants  of  the  penguin,  first  to  become 
enabled  to  flap  along  the  surface  of  the  sea  like  the  logger- 
headed  duck,  and  ultimately  to  rise  from  its  surface  and 
glide  through  the  air? 

I  will  now  give  a  few  examples  to  illustrate  the  fore¬ 
going  i.emaiks,  and  to  show  how  liable  we  are  to  error  in 
supposing  that  whole  groups  of  species  have  suddenly  been 
pioduced.  Even  in  so  short  an  interval  as  that  between 
the  first  and  second  editions  of  PictePs  great  work  on 
Palaeontology,  published  in  1844-4G  and  in  1853-57,  the 
conclusions  on  the  .  first  appearance  and  disappearance  of 
several  gioups  of  animals  have  been  considerably  modified* 
and  a  third  edition  would  require  still  further  changes.  I  may 
recall  the  well-known  fact  that  in  geological  treatises,  pub- 
hshed  not  many  years  ago,  mammals  were  always  spoken 
of  as  having  abruptly  come  in  at  the  commencement  of  the 
tertiary  series.  And  now  one  of  the  richest  known  ac¬ 
cumulations  of  fossil  mammals  belongs  to  the  middle  of  the 
secondary  series;  and  true  mammals  have  been  discovered 
in. the  new  red  sandstone  at  nearly  the  commencement  of 
this  great  series.  Cuvier  used  to  urge  that  no  monkey 
occurred  in  any  tertiary  stratum;  but  now  extinct  species 
have  been  discovered  in  India,  South  America  and  in 
Euiope,  as  far  back  as  the  miocene  stage.  Had  it  not 
been  for  the  rare  accident  of  the  preservation  of  footsteps 
in  the  new  red  sandstone  of  the  United  States,  who  would 
have  ventured  to  suppose  that  no  less  than  at  least  thirty 
different  bird-like  animals,  some  of  gigantic  size,  existed 
duimg  that  period?  Uot  a  fragment  of  bone  has  been  dis¬ 
covered.  in  these  beds.  Uot  long  ago,  palaeontologists 
maintained  that  the  whole  class  of  birds  came  suddenly 
into  existence  during  the  eocene  period;  but  now  we  know, 
on  the  authority  of  Professor  Owen,  that  a  bird  certainly 
h\ed  during  the  deposition  of  the  upper  greensand;  and 
still  moie  recently,  that  strange  bird,  the  Archeopteryx, 


336 


SUDDEN  APPEARANCE  OE 


with  a  long  lizard-like  tail,  bearing  a  pair  of  feathers  on 
each  joint,  and  with  its  wings  furnished  with  two  free 
claws,  has  been  discovered  in  the  oolitic  slates  of  Solenho- 
fen.  Hardly  any  recent  discovery  shows  more  forcibly 
than  this  how  little  we  as  yet  know  of  the  former  inhab¬ 
itants  of  the  world. 

I  may  give  another  instance,  which,  from  having  passed 
under  my  own  eyes,  has  much  struck  me.  In  a  memoir  on 
Fossil  Sessile  Cirripedes,  I  stated  that,  from  the  large  num¬ 
ber  of  existing  and  extinct  tertiary  species;  from  the  ex¬ 
traordinary  abundance  of  the  individuals  of  many  species 
all  over  the  world,  from  the  Arctic  regions  to  the  equator, 
inhabiting  various  zones  of  depths,  from  the  upper  tidal 
limits  to  fifty  fathoms;  from  the  perfect  manner  in  which 
specimens  are  preserved  in  the  oldest  tertiary  beds;  from 
the  ease  with  which  even  a  fragment  of  a  valve  can  be 
recognized;  from  all  these  circumstances,  I  inferred  that, 
had  sessile  cirripedes  existed  during  the  secondary  periods, 
they  would  certainly  have  been  preserved  and  dis¬ 
covered;  and  as  not  one  species  had  then  been,  discov¬ 
ered  in  beds  of  this  age,  I  concluded  that  this  great 
group  had  been  suddenly  developed  at  the  commencement 
of  the  tertiary  series.  This  was  a  sore  trouble  to  me, 
adding,  as  I  then  thought,  one  more  instance  of  the 
abrupt  appearance  of  a  great  group  of  species.  But  my 
work  had  hardly  been  published,  when  a  skillful  palaeon- 
togist,  M.  Bosquet,  sent  me  a  drawing  of  a  perfect  speci¬ 
men  of  an  unmistakable  sessile  cirripede,  which  he  had 
himself  extracted  from  the  chalk  of  Belgium.  And,  as 
if  to  make  the  case  as  striking  as  possible,  this  cirripede 
was  a  Ohthamalus,  a  very  common,  large,  and  ubiquitous 
genus,  of  which  not  one  species  has  as  yet  been  found  even 
in  any  tertiary  stratum.  Still  more  recently,  a  Pyrgoma, 
a  member  of  a  distinct  subfamily  of  sessile  cirripedes,  has 
been  discovered  by  Mr.  Woodward  in  the  upper  chalk;  so 
that  we  now  have  abundant  evidence  of  the  existence  of 
this  group  of  animals  during  the  secondary  period. 

The  case  most  frequently  insisted  on  by  palaeontologists 
of  the  apparently  sudden  appearance  of  a  whole  group  of 
species,  is  that  of  thet  eleostean  fishes.,  low  down,  according 
to  Agassiz,  in  the  Chalk  period.  This  group  includes  the 
large  majority  of  existing  species.  But  certain  J urassic 


GROUPS  OF  ALLIED  SPECIES . 


33? 


and  Triassic  forms  are  now  commonly  admitted  to  be 
teleostean;  and  even  some  palaeozoic  forms  have  thus  been 
classed  by  one  high  authority.  If  the  teleosteans  had 
really  appeared  suddenly  in  the  northern  hemisphere  at 
the  commencement  of  the  chalk  formation,  the  fact  would 
have  been  highly  remarkable;  but  it  would  not  have  formed 
an  insuperable  difficulty,  unless  it  could  likewise  have  been 
shown  that  at  the  same  period  the  species  were  suddenly 
and  simultaneously  developed  in  other  quarters  of  the 
world.  It  is  almost  superfluous  to  remark  that  hardly  any 
fossil-fish  are  known  from  south  of  the  equator;  and  by 
running  through  Pictet's  Palaeontology  it  will  be  seen  that 
very  few  species  are  known  from  several  formations  in 
Europe.  Some  few  families  of  fish  now  have  a  confined 
range;  the  teleostean  fishes  might  formerly  have  had  a 
similarly  confined  range,  and  after  having  been  largely 
developed  in  some  one  sea,  have  spread  widely.  Nor  have 
we  any  right  to  suppose  that  the  seas  of  the  world  have 
always  been  so  freely  open  from  south  to  north  as  they  are 
at  present.  Even  at  this  day,  if  the  Malay  Archipelago 
were  converted  into  land,  the  tropical  parts  of  the  Indian 
Ocean  would  form  a  large  and  perfectly  inclosed  basin,  in 
which  any  great  group  of  marine  animals  might  be  multi¬ 
plied;  and  here  they  would  remain  confined,  until  some  of 
the  species  became  adapted  to  a  cooler  climate,  and  were 
enabled  to  double  the  southern  capes  of  Africa  or  Australia, 
and  thus  reach  other  and  distant  seas. 

From  these  considerations,  from  our  ignorance  of  the 
geology  of  other  countries  beyond  the  confines  of  Europe 
and  the  United  States,  and  from  the  revolution  in  oar 
palaeontological  knowledge  effected  by  the  discoveries  of 
the  last  dozen  years,  it  seems  to  me  to  be  about  as  rash 
to  dogmatize  on  the  succession  of  organic  forms  throughout 
the  world,  as  it  would  be  for  a  naturalist  to  land  for  five 
minutes  on  a  barren  point  in  Australia,  and  then  to  discuss 
the  number  and  range  of  its  productions. 

OK  THE  SUDDEK  APPEARAKCE  OF  GROUPS  Ov  ALLIED 
SPECIES  IK  THE  LOWEST  KKOWK  FOSSILIFEROUS  STRATA. 

There  is  another  and  allied  difficulty,  which  is  much 
,  more  serious,  I  allude  to  the  manner  in  which  species 


338 


GROUPS  OF  ALLIED  SPECIES 


belonging  to  several  of  the  main  divisions  of  the  animal 
kingdom  suddenly  appear  in  the  lowest  known  fossiliferous 
rocks.  Most  of  the  arguments  which  have  convinced  me 
that  all  the  existing  species  of  the  same  group  are  descended 
from  a  single  progenitor,  apply  with  equal  force  to  the 
earliest  known  species.  For  instance,  it  cannot  be  doubted 
that  all  the  Cambrian  and  Silurian  trilobites  are  descended 
from  some  one  crustacean,  which  must  have  lived  long 
before  the  Cambrian  age,  and  which  probably  differed 
greatly  from  any  known  animal.  Some  of  the  most  ancient 
animals,  as  the  Nautilus,  Lingula,  etc.,  do  not  differ  much 
from  living  species;  and  it  cannot  on  our  theory  be  sup¬ 
posed,  that  these  old  species  were  the  progenitors  of  all  the 
species  belonging  to  the  same  groups  which  have  subse¬ 
quently  appeared,  for  they  are  not  in  any  degree  inter¬ 
mediate  in  character. 

Consequently,  if  the  theory  be  true,  it  is  indisputable 
that  before  the  lowest  Cambrian  stratum  was  deposited 
long  periods  elapsed,  as  long  as,  or  probably  far  longer 
than,  the  whole  interval  from  the  Cambrian  age  to  the 
present  day;  and  that  during  these  vast  periods  the  world 
swarmed  with  living  creatures.  Here  we  encounter  a 
formidable  objection;  for  it  seems  doubtful  whether  the 
earth,  in  a  fit  state  for  the  habitation  of  living  creatures, 
has  lasted  long  enough.  Sir  W.  Thompson  concludes  that 
the  consolidation  of  the  crust  can  hardly  have  occurred  less 
than  twenty  or  more  than  four  hundred  million  years  ago, 
but  probably  not  less  than  ninety-eight  or  more  than  two 
hundred  million  years.  These  very  wide  limits  show  how 
doubtful  the  data  are;  and  other  elements  may  have  here¬ 
after  to  be  introduced  into  the  problem.  Mr.  Croll  esti¬ 
mates  that  about  sixty  million  years  have  elapsed  since  the 
Cambrian  period,  but  this,  judging  from  the  small  amount 
of  organic  change  since  the  commencement  of  the  Glacial 
epoch,  appears  a  very  short  time  for  the  many  and  great 
mutations  of  life,  which  have  certainly  occurred  since  the 
Cambrian  formation;  and  the  previous  one  hundred  and 
forty  million  years  can  hardly  be  considered  as  sufficient 
for  the  development  of  the  varied  forms  of  life  which 
already  existed  during  the  Cambrian  period.  It  is,  how¬ 
ever,  probable,  as  Sir  William  Thompson  insists,  that  the 
world  at  a  very  early  period  was  subjected  to  more  rapid 


/iY  LO  WERT  EOSSILIFERO  t)8  STRA TA.  339 

;,tS  Puhysical  con<3’tions  than  those 
induce  changes  at  a  «  ° 1  chal!?es  woultl  have  tended  to 
which  then  existed.  COrreSp°Ddl^  rate  in  organisms 

To  the  question  why  we  do  not  find  rich  fossil  if erons 
H  Pplts  belonging  to  these  assumed  earliest  periods  prior  to 
the  Cambrian  system,  I  can  give  no  satisfactory  Answer 
Seveial  eminent  geologists,  with  Sir  R.  Murchison  at  their 
head,  were  until  recently  convinced  that  we  beheld  in  the 

dTwn  of  Sr'othe  ‘r  ,’r6St  Siluri“  stratum  the"  first 
i  0  lite  Othei  highly  competent  judges,  as  Lyell  and 

ha^e  dlsPuted  tlils  conclusion.  We  should  not 
foiget  than  only  a  small  portion  of  the  world  is  known  with 
accuracy.  Not  very  long  ago  M.  Barrande  added  another 
and  lower  stage,  abounding  with  new  and  peculiar  s wr  it 
eneath  the.  then  known  Silurian  system;  and  now  still 
ower  down  m  the  Lower  Cambrian  formation  Mr  Hicks 
has  found  South  Wales  beds  rich  in  trilobites  and  con 
taming  various  molluscs  and  annelids.  The  presence  of 
p  losphatio  nodules  and  bituminous  matter,  even  in  some 
ot  the  lowest  azotm  rocks,  probabty  indicates  life  at  these 

formaLou 1 of  p®  efst.ence  of  tde  Eozoon  in  the  Laurentian 
formation  of  Canada  is  generally  admitted.  There  are  three 

gi eat^ series  of  strata  beneath  the  Silurian  system  in  Can¬ 
ada,  m  the  lowest  of  which  the  Eozoon  is  found.  Sir  W 

forgsurmstseSthtaiftcfhen  ltUnited  tllickuess  >nay  possibly 

base  of  tlm  nal  La  •  the  ?uoceedmS  rocks,  from  the 
oase  ot  the  palaeozoic  series  to  the  present  time 

Ye  are  thus  carried  back  to  a  period  so  remote  that  the 

appearance  of  the  so-called  primordial  fauna  (of  Barrande) 

evtnt  ”  The6  EoLo°Tdred  fV?  comparatively  modern 
event  The  Eozoon  belongs  to  the  most  lowly  organized 

bUt  iSi  h!ghly  0^nized°for  its 

has  rema,  tetl  el^t  ?  1  tleSS  nilmbers-  a,ld-  as  Dr.  Dawson 
has  rema  ked,  ceitainly  preyed  on  other  minute  organic 

mgs,  which  must  have  lived  in  great  numbers  Thus 

he  words,  which  I  wrote  in  1859,  about  the  existence  of 

mg  beings  long  before  the  Cambrian  period  and  which 

are  almost  the  same  with  those  since  used  bv  Sir  W  Lo<ran* 

have  proved  true  Nevertheless,  the  difficulty  of  assigning 

any  good  reason  for  the  absence  of  vast  piles  of  strata  rich 

in  fossils  beneath  the  Cambrian  system  is  very  great.  It 


340 


GROUPS  OF  ALLIED  SPECIES 


does  not  seem  probable  that  the  most  ancient  beds  ha\e 
been  quite  worn  away  by  denudation,  or  that  their  fossils 
have  been  wholly  obliterated  by  metamorphic  action,  for 
if  this  had  been  the  case  we  should  have  found  only  small 
remnants  of  the  formations  next,  succeeding  them  in  age, 
and  these  would  always  have  existed  in  a  partially  meta¬ 
morphosed  condition.  But  the  descriptions  which  we 
possess  of  the  Silurian  deposits  over  immense  territories  in 
Russia  and  in  North  America,  do  not  support  the  view 
that  the  older  a  formation  is  the  more  invariably  it  has 
suffered  extreme  denudation  and  metamorphism. 

The  case  at  present  must  remain  inexplicable,  and  may 
be  truly  urged  as  a  valid  argument  against  the  views  here 
entertained.  To  show  that  it  may  hereafter  receive  some 
explanation,  I  will  give  ,  the  following  hypothesis.  From 
the  nature  of  the  organic  remains  which  do  not  appear  to 
have  inhabited  profound  depths,  in  the  several  formations 
of  Europe  and  of  the  United  States;  and  from  the  amount 
of  sediment,  miles  in  thickness,  of  which  the  formations 
are  composed,  we  may  infer  that  from  first  to  last  large 
islands  or  tracts  of  land,  whence  the  sediment  was  derived, 
occurred  in  the  neighborhood  of  the  now  existing  conti¬ 
nents  of  Europe  and  North  America,  ihis  same  view  has 
since  been  maintained  by  Agassiz  and  others.  But  we  do 
not  know  what  was  the  state  of  things  in  the  intervals 
between  the  several  successive  formations;  whether  Europe 
and  the  United  States  during  these  intervals  existed .  as 
dry  land,  or  as  a  submarine  surface  near  land,  on  which 
sediment  was  not  deposited,  or  as  the  bed  of  an  open  and 
unfathomable  sea. 

Looking  to  the  existing  oceans,  which  are  thrice  as  ex¬ 
tensive  as  the  land,  we  see  them  studded  with  many  islands; 
but  hardly  one  truly  oceanic  island  (with  the  exception  of 
New  Zealand,  if  this  can  be  called  a  truly  oceanic  island) 
is  as  yet  known  to  afford  even  a  remnant  of  any  palaeozoic 
or  secondary  formation.  Hence,  we  may  perhaps  infer, 
that  during  the  palaeozoic  and  secondary  periods,  neither 
continents  nor  continental  islands  existed  where  our  oceans 
now  extend;  for  had  they  existed,  palaeozoic  and  second- 
arv  formations  would  in  all  probability  have  been  accumu¬ 
lated  from  sediment  derived  from  their  wear  and  tear; 
and  these  would  have  been  at  least  partially  upheaved  by 


IN  LO  WEST  F0SSIL1FER0  VS  STRA  TA.  345. 

the  oscillations  of  level,  which  must  have  intervened 
during  these  enormously  long  periods.  If,  then,  we  may 
infer  anything  from  these  facts,  we  may  infer  that,  where 
our  oceans  now  extend,  oceans  have  extended  from  the 
remotest  period  of  which  we  have  any  record;  and  on 
the  other  h*$nd,  that  where  continents  now  exist, 
large  tracts  of  land  have  existed,  subjected,  no  doubt,  to 
gieat  oscillations  of  level,  since  the  Cambrian  period.  The 
colored  map  appended  to  my  volume  on  Coral  Reefs,  led 

great  oceans  are  still  mainly  areas 
01  subsidence,  the  great  archipelagoes  still  areas  of  oscilla¬ 
tions  of  level,  and  the  continents  areas  of  elevation.  JBut 
we  have  no  reason  to  assume  that  things  have  thus  re¬ 
mained  from  the  beginning  of  the  world.  Our  continents 
seem  to  have  been  formed  by  a  preponderance,  during 
many  oscillations  of  level,  of  the  force  of  elevation.  But 
may  not  the  areas  of  preponderant  movement  have 
changed  in  the  lapse  of  ages?  At  a  period  long  antecedent 
to  the  Cambrian  epoch,  continents  may  have  existed  where 
oceans  are  now  spread  out,  and  clear  and  open  oceans 
may  have  existed  where,  our  continents  now  stand.  Nor 
should  we  be  justified  in  assuming  that  if,  for  instance, 
the  bed  of  the  Pacific  Ocean  were  now  converted  into  a 
continent  we  should  there  find  sedimentary  formations,  in 
recognizable  condition,  older  than  the  Cambrian  strata, 
supposing  such  to  have  been  formerly  deposited;  for  it 
might  well  happen  that  strata  which  had  subsided  some 
miles  nearer  to  the  center  of  the  earth,  and  which  had 
been  pressed  on  by  an  enormous  weight  of  superincumbent 
water,  might  have  undergone  far  more  metamorphic  action 
than  strata  which  have  always  remained  nearer  to  the  sur¬ 
face.  The  immense  areas  in  some  parts  of  the  world,  for 
instance  in  South  America,  of  naked  metamorphic  rocks, 
which  must  have  been  heated  under  great  pressure,  have 
always  seemed  to  me  to  require  some  special  explana¬ 
tion;  and  we  may  perhaps  believe  that  we  see  in  these 
large  areas  the  many  formations  long  anterior  to  the  Cam¬ 
brian  epoch  in  a  completely  metamorphosed  and  denuded 
condition. 

The  several  difficulties  here  discussed,  namely,  that, 
though  we  find  in  our  geological  formations  many  links 
between  the  species  which  now  exist  and  which  formerly 


342 


GROUPS  OF  ALLIED  SPECIES. 


existed,  we  do  not  find  infinitely  numerous  fine  transitional 
forms  closely  joining  them  ail  together.  The  sudden  man¬ 
ner  in  which  several  groups  of  species  first  appear  in  our 
European  formations,  the  almost  entire  absence,  as  at 
nresent  known,  of  formations  rich  in  fossils  beneath 
the  Cambrian  strata,  are  all  undoubtedly  of  the  most 
serious  nature.  We  see  this  in  the  fact  that  the  most  em¬ 
inent  palaeontologists,  namely,  Cuvier,  Agassiz,  Bariande, 
Pictet/ Falconer,  E.  Forbes,  etc.,  and  all  our  greatest  geol¬ 
ogists,  as  Lyell,  Murchison,  Sedgwick  etc.,  have  unani¬ 
mously,  often  vehemently,  maintained  the  immutability  of 
species  But  Sir  Charles  Lyell  now  gives  the  support  of 
his  high  authority  to  the  opposite  side,  and  most  geologists 
and  palaeontologists  are  much  shaken  in  their  formei  belief.. 
Those  who  believe  that  the  geological  record  is  in  any  de¬ 
gree  perfect,  will  undoubtedly  at  once  reject  the  theory, 
For  my  part,  following  out  Ly ell’s  metaphor,  I  look  at  the 
geological  record  as  a  history  of  the  world  imperfectly  kept 
Ld  written  in  a  changing  dialect.  Of  this  history  we  pos¬ 
sess  the  last  volume  alone,  relating  only  to  two  or  three 
countries.  Of  this  volume,  only  here  and  there  a  short 
chapter  has  been  preserved,  and  of  each  page,  only  here 
and  there  a  few  lines.  Each  word  of  the  slowly-changing 
language,  more  or  less  different  in  the  successive  chapters, 
may  represent  the  forms  of  life,  which  are  entombed  in 
on/  consecutive  formations,  and  which  falsely  appear 
to  have  been  abruptly  introduced.  On  this  view  the 
difficulties  above  discussed  are  greatly  diminished  or  even 

disappear. 


ORGANIC  BEINGS. 


343 


CHAPTER  XL 

ON  THE  GEOLOGICAL  SUCCESSION  OF  ORGANIC  BEINGS. 

^  S^0W  an(^  successive  appearance  of  new  species — On  tlieir 
different  rates  of  change — Species  once  lost  do  not  reappear — 
Groups  of  species  follow  the  same  general  rules  in  their  appear¬ 
ance  and  disappearance  as  do  single  species — On  extinction — On 
simultaneous  changes  in  the  forms  of  life  throughout  the 
world  On  the  affinities  of  extinct  species  to  each  other  and  to 
living  species  -On  the  state  of  development  of  ancient  forms— 
On  the  succession  of  the  same  types  within  the  same  areas— 
Nummary  of  preceding  and  present  chapter. 

Let  us  now  see  whether  the  several  facts  and  laws 
relating  to  the  geological  succession  of  organic  beings 
accord  best  with  the  common  view  of  the  immutability  of 
species,  or  with  that  of  their  slow  and  gradual  modifica¬ 
tion,  through  variation  and  natural  selection. 

New  species  have  appeared  very  slowly,  one  after  another, 
both  on  the  land  and  in  the  waters.  Lyell  has  shown  that 
it  is  hardly  possible  to  resist  the  evidence  on  this  head  in 
the  case  of  the  several  tertiary  stages;  and  every  year  tends 
to  fill  up  the  blanks  between  the  stages,  and  to  make  the 
proportion  between  the  lost  and  existing  forms  more 
gradual.  In  some  of  .  the  most  recent  beds,  though 
undoubtedly  of  high  antiquity  if  measured  by  years,  only 
one  or  two  species  are  extinct,  and  only  one  or  two  are  new, 
having  appeared  there  for  the  first  time,  either  locally,  or' 
as  far  as  we  know,  on  the  face  of  the  earth.  The  second¬ 
ary  formations  are  more  broken;  but,  as  Bronn  has 
remarked,  neither  the  appearance  nor  disappearance  of  the 
many  species  embedded  in  each  formation  has  been  simul¬ 
taneous. 

Species  belonging  to  different  genera  and  classes  have 
not  changed  at  the  same  rate,  or  in  the  same  degree.  In 
the  older  tertiary  beds  a  few  living  shells  may  still  be 
found  in  the  midst  of  a  multitude  of  extinct  forms. 


344 


TEE  GEOLOGICAL  SUCCESSION 


Falconer  lias  given  a  striking  instance  of  a  similar  fact, 
for  an  existing  crocodile  is  associated  with  many  lost 
mammals  and  reptiles  in  the  sub- Himalayan  deposits. 
The  Silurian  Lingula  differs  but  little  from  the  living 
species  of  this  genus;  whereas  most  of  the  other  Silurian 
Molluscs  and  all  the  Crustaceans  have  changed  greatly. 
The  productions  of  the  land  seem  to  have  changed  at  a 
quicker  rate  than  those  of  the.  sea,  of  which  a  striking 
instance  has  been  observed  in  Switzerland.  There  is  some 
reason  to  believe  that  organisms  high  in  the  scale,  change 
more  quickly  than  those  that  are  low:  though  there  are 
exceptions  to  this  rule.  The  amount  of  organic  change, 
as  Pictet  has  remarked,  is  not  the  same  in  each  successive 
so-called  formation.  Yet  if  we  compare  any  but  the  most 
closely  related  formations,  all  the  species  will.be  found  to 
have  undergone  some  change.  When  a  species  has  once 
disappeared  from  the  face  of  the  earth,  we  have  no  reason 
to  believe  that  the  same  identical  form  ever  reappears. 
The  strongest  apparent  exception  to  this  latter  rule  is  that 
of  the  so-called  “  colonies  ”  of  M.  Barrande,  which  intrude 
for  a  period  in  the  midst  of  an  older  formation,  and  then 
allow  the  pre-existing  fauna  to  reappear;  but  LyelTs  expla¬ 
nation,  namely,  that  it  is  a  case  of  temporary  migration 
from  a  distinct  geographical  province,  seems  satisfactory. 

These  several  facts  accord  well  with  our  theory,  which 
includes  no  fixed  law  of  development,  causing  all  the 
inhabitants  of  an  area  to  change  abruptly,  or  simultane¬ 
ously,  or  to  ail  equal  degree.  The  process  of  modification 
must  be  slow,  and  will  generally  affect  only  a  few  species 
at  the  same  time;  for  the  variability  of  each  species  is 
independent  of  that  of  all  others.  Whether  such  varia¬ 
tions  or  individual  differences  as  may  arise  will  be  accu¬ 
mulated  through  natural  selection  in  a  greater  or  less 
degree,  thus  causing  a  greater  or  less  amount  of  perma¬ 
nent  modification,  will  depend  on  many  complex  contin¬ 
gencies — on  the  variations  being  of  a  beneficial  nature,  on 
the  freedom  of  intercrossing,  on  the  slowly  changing 
physical  conditions  of  the  country,  on  the  immigration  of 
new  colonists,  and  on  the  nature  of  the  other  inhabitants 
with  which  the  varying  species  come  into  competition. 
Hence  it  is  by  no  means  surprising  that  one  species  should 
retain  the  same  identical  form  much  longer  than  others; 


OF  ORGANIC  BEINGS. 


345 


or,  if  changing,  should  change  in  a  less  degree.  We  find 
similar  relations  between  the  existing  inhabitants  of  dis¬ 
tinct  countries;  for  instance,  the  land -shells  and  coleopter¬ 
ous  insects  of  Madeira  have  come  to  differ  considerably 
from  their  nearest  allies  on  the  continent  of  Europe, 
whereas  the  marine  shells  and  birds  have  remained 
unaltered.  We  can  perhaps  understand  the  apparently 
t  quicker  rate  of  change  in  terrestrial  and  in  more  highly 
'organized  productions  compared  with  marine  and  lower 
productions,  by  the  more  complex  relations  of  the  higher 
beings  to  their  organic  and  inorganic  conditions  of  life,  as 
explained  in  a  former  chapter.  When  many  of  the  inhab¬ 
itants  of  any  area  have  become  modified  and  improved,  we 
can  understand,  on  the  principle  of  competition,  and  from 
the  all-important  relations  of  organism  to  organism  in  the 
struggle  for  life,  that  any  form  which  did  not  become  in 
some  degree  modified  and  improved,  would  be  liable  to 
extermination.  Hence,  we  see  why  all  the  species  in  the 
same  region  do  at  last,  if  we  look  to  long  enough  intervals 
of  time,  become  modified,  for  otherwise  they  would  become 
extinct. 

In  members  of  the  same  class  the  average  amount  of 
change,  during  long  and  equal  periods  of  time,  may,  per¬ 
haps,  be  nearly  the  same;  but  as  the  accumulation  of 
enduring  formations,  rich  in  fossils,  depends  on  great 
masses  of  sediment  being  deposited  on  subsiding  areas,  our 
formations  have  been  almost  necessarily  accumulated  at 
wide  and  irregularly  intermittent  intervals  of  time;  conse¬ 
quently  the  amount  of  organic  change  exhibited  by  the  fos¬ 
sils  embedded  in  consecutive  formations  is  not  equal. 
Each  formation,  on  this  view,  does  not  mark  a  new  and 
complete  act  of  creation,  but  only  an  occasional  scene, 
taken  almost  at  hazard,  in  an  ever  slowly  changing  drama. 

We  can  clearly  understand  why  a  species  when  once  lost 
should  never  reappear,  even  if  the  very  same  conditions  of 
life,  organic  and  inorganic,  should  recur.  For  though  the 
offspring  of  one  species  might  be  adapted  (and  no  doubt 
this  has  occurred  in  innumerable  instances)  to  fill  the 
place  of  another  species  in  the  economy  of  nature,  and 
thus  supplant  it;  yet  the  two  forms — the  old  and  the 
new — "would  not  be  identically  the  same;  for  both  would 
almost  certainly  inherit  different  characters  from  their  dk- 


346 


TEE  GEOLOGICAL  SUCCESSION 


tinct  progenitors;  and  organisms  already  differing  would 
vary  in  a  different  manner.  For  instance,  it  is  possible,  if 
all  our  fantail  pigeons  were  destroyed,  that  fanciers  might 
make  a  new  breed  hardly  distinguishable  from  the  present 
breed;  but  if  the  parent  rock-pigeon  were  likewise  destroyed, 
and  under  nature  we  have  every  reason  to  believe  that 
parent  forms  are  generally  supplanted  and  exterminated  by 
their  improved  offspring,  it  is  incredible  that  a  fantail, 
identical  with  the  existing  breed,  could  be  raised  from  any 
other  species  of  pigeon,  or  even  from  any  other  well  estab¬ 
lished  race  of  the  domestic  pigeon,  for  the  successive  varia¬ 
tions  would  almost  certainly  be  in  some  degree  different, 
and  the  newly-formed  variety  would  probably  inherit  from 
its  progenitor  some  characteristic  differences. 


Groups  of  species,  that  this,  genera  and  families,  follow 
the  same  general  rules  in  their  appearance  and  disappear¬ 
ance  as  do  single  species,  changing  more  or  less  quickly, 
and  in  a  greater  or  lesser  degree.  A  group,  when  it  has 
once  disappeared,  never  reappears;  that  is,  its  existence,  as 
long  as  it  lasts,  is  continuous.  I  am  aware  that  there  are 
some  apparent  exceptions  to  this  rule,  but  the  exceptions 
are  surprisingly  few,  so  few  that  E.  Forbes,  Pictet,  and 
Woodward  (though  all  strongly  opposed  to  such  views  as  I 
maintain)  admit  its  truth;  and  the  rule  strictly  accords 
with  the  theory.  For  all  the  species  of  the  same  group, 
however  long  it  may  have  lasted,  are  the  modified  descend¬ 
ants  one  from  the  other,  and  all  from  a  common  progeni¬ 
tor.  In  the  genus  Lingula,  for  instance,  the  species 
which  have  successively  appeared  at  all  ages  must  have 
been  connected  by  an  unbroken  series  of  generations,  from 
the  lowest  Silurian  stratum  to  the  present  day. 

We  have  seen  in  the  last  chapter  that  whole  groups  of 
species  sometimes  falsely  appear  to  have  been  abruptly 
developed;  and  I  have  attempted  to  give  an  explanation  of 
this  fact,  which  if  true  would  be  fatal  to  my  views.  But 
such  cases  are  certainly  exceptional;  the  general  rule  being 
a  gradual  increase  in  number,  until  the  group  reaches  its 
maximum,  and  then,  sooner  or  later,  a  gradual  decrease. 
If  the  number  of  the  species  included  within  a  genus,  or 
the  number  of  the  genera  within  a  family,  be  represented 
by  a  vertical  line  of  varying  thickness,  ascending  through 
the  successive  geological  formations,  in  which  the  species 


OF  ORGANIC  BEINGS. 


347 

are  found,  the  line  will  sometimes  falsely  appear  to  begin 
at  its  lower  end,  not  in  a  sharp  point,  but  abruptly;  it 
then  gradually  thickens  upward,  often  keeping  of  equal 
thickness  for  a  space,  and  ultimately  thins  out  in  the 
upper  beds,  marking  the  decrease  and  final  extinction  of 
the  species.  This  gradual  increase  in  number  of  the  species 
of  a  group  is  strictly  conformable  with  the  theory,  for  the 
species  of  the  same  genus,  and  the  genera  of  the  same 
family,  can  increase  only  slowly  and  progressively;  the 
process  of  modification  and  the  production  of  a  number  of 
allied  forms  necessarily  being  a  slow  and  gradual  process, 
one  species  first  giving  rise  to  two  or  three  varieties,  these 
being  slowly  converted  into  species,  which  in  their  turn 
produce  by  equally  slow  steps  other  varieties  and  species, 
and  so  on,  like  the  branching  of  a  great  tree  from  a  single 
stem,  till  the  group  becomes  large. 

<W  EXTI^CTICW. 

We  have  as  yet  only  spoken  incidentally  of  the  disap¬ 
pearance  of  species  and.  of  groups  of  species.  On  the 
theory  of  natural  selection,  •  the  extinction  of  old  forms 
and  the  production  of  new  and  improved  forms  are  inti¬ 
mately  connected  together,.  The  old  notion  of  all  the 
inhabitants  of  the  earth  having  been  swept  away  by  catas¬ 
trophes  at  successive  periods  is  very  generally  given  up,  even 
by  those  geologists,  as  Elie  de  Beaumont,  Murchison,  Bar- 
rande,  etc.,  whose  general  views  would  naturally  lead 
them  to  this  conclusion.  On  the  contrary,  we  have  every 
reason  to  believe,  from  the  study  of  the  tertiary  formations, 
that  species  and  groups  of  species  gradually  disappear,  one 
after  another,  first  from  one  spot,  then  from  another,  and 
finally  from  the  world.  In  some  few  cases,  however,  as  by 
the  breaking  of  an  isthmus  and  the  consequent  irruption 
of  a  multitude  of  new  inhabitants  into  an  adjoining  sea, 
or  by.  the  final  subsidence  of  an  island,  the  process  of  ex¬ 
tinction  may  have  been  rapid.  Both  single  species  and 
whole  groups  of  species  last  for  very  unequal  periods;  some 
groups,  as  we  have  seen,  have  endured  from  the  earliest 
known  dawn  of  life  to  the  present  day;  some  have  disap¬ 
peared  before  the  close  of  the  palaeozoic  period.  No  fixed 
law  seems  to  determine  the  length  of  time  during  which 


348 


EXTINCTION. 


any  single  species  or  any  single  genus  endures.  There  is 
reason  to  believe  that  the  extinction  of  a  whole  group  of 
species  is  generally  a  slower  process  than  their  production: 
if  their  appearance  and  disappearance  be  represented,  as 
before,  by  a  vertical  line  of  varying  thickness  the  line  is 
found  to  taper  more  gradually  at  its  upper  end,  which 
marks  the  progress  of  extermination,  than  at  its  lower  end, 
which  marks  the  first  appearance  and  the  early  increase  in 
number  of  the  species.  In  some  cases,  however,  the  extermi¬ 
nation  of  whole  groups,  as  of  ammonites,  toward  the  close 
of  the  secondary  period,  has  been  wonderfully  sudden. 

The  extinction  of  species  has  been  involved  in  the  most 
gratuitous  mystery.  Some  authors  have  even  supposed 
that,  as  the  individual  has  a  definite  length  of  life,  so  have 
species  a  definite  duration.  No  one  can  have  marvelled 
more  than  I  have  done  at  the  extinction  of  species.  When 
I  found  in  La  Plata  the  tooth  of  a  horse  embedded  with 
the  remains  of  Mastodon,  Megatherium,  Toxodon  and 
other  extinct  monsters,  which  all  co-existed  with  still 
living  shells  at  a  very  late  geological  period,  I.  was.  filled 
with  astonishment;  for,  seeing  that  the  horse,  since  its  in¬ 
troduction  by  the  Spaniards  into  South  America,  has  run 
wild  over  the  whole  country  and  has  increased  in  numbers 
at  an  unparalleled  rate,  I  asked  myself  what  could  so.  re¬ 
cently  have  exterminated  the  former  horse  under  conditions 
of  life  apparently  so  favorable.  But  my  astonishment  was 
groundless.  Professor  Owen  soon  perceived  that  the  tooth, 
though  so  like  that  of  the  existing  horse,  belonged  to  an 
extinct  species.  Had  this  horse  been  still  living,  but  in 
some  degree  rare,  no  naturalist  would  have  felt  the  least 
surprise  at  its  rarity;  for  rarity  is  the  attribute  of  a  vast 
number  of  species  of  all  classes,  in  all  countries.  If  we 
ask  ourselves  why  this  or  that  species  is  rare,  we.  answer 
that  something  is  unfavorable  in  its  conditions  of  life;  but 
what  that  something  is  we  can  hardly  ever  tell.  On  the 
supposition  of  the  fossil  horse  still  existing  as  a  rare  species, 
we  might  have  felt  certain,  from  the  analogy  of  all  other 
mammals,  even  of  the  slow-breeding  elephant,  and  from  the 
history  of  the  naturalization  of  the  domestic  horse  in 
South  America,  that  under  more  favorable  conditions  it 
would  in  a  very  few  years  have  stocked  the  whole  con¬ 
tinent.  But  we  could  not  have  told  what  the  unfavorable 


EXTINCTION. 


340 


conditions  were  which  checked  its  increase,  whether  some 
one  or  several  contingencies,  and  at  what  period  of  the 
horse’s  life,  and  in  what  degree  they  severally  acted.  If 
the  conditions  had  gone  on,  however  slowly,  becoming  less 
and  less  favorable,  we  assuredly  should  not  have  perceived 
the  fact,  yet  the  fossil  horse  would  certainly  have  become 
rarer  and  rarer,  and  finally  extinct — its  place  being  seized 
on  by  some  more  successful  competitor. 

It  is  most  difficult  alwavs  to  remember  that  the  increase 
of  every  creature  is  constantly  being  checked  by  unper¬ 
ceived  hostile  agencies;  and  that  these  same  unper¬ 
ceived  agencies  are  amply  sufficient  to  cause  rarity,  and 
finally  extinction.  So  little  is  this  subject  understood, 
that  I  have  heard  surprise  repeatedly  expressed  at  such 
great  monsters  as  the  Mastodon  and  the  more  ancient  Din- 
osaurians  having  become  extinct;  as  if  mere  bodily  strength 
gave  victory  in  the  battle  of  life.  Mere  size,  on  the  con¬ 
trary,  would  in  some  cases  determine,  as  has  been  remarked 
by  Owen,  quicker  extermination,  from  the  greater  amount 
of  requisite  food.  Before  man  inhabited  India  or  Africa, 
some  cause  must  have  checked  the  continued  increase  of 
the  existing  elephant.  A  highly  capable  judge.  Dr.  Fal¬ 
coner,  believes  that  it  is  chiefly  insects  which,  from  inces¬ 
santly  harassing  and  weakening  the  elephant  in  India, 
check  its  increase;  and  this  was  Bruce’s  conclusion  with 
respect  to  the  African  elephant  in  Abyssinia.  It  is  certain 
that  insects  and  blood-sucking  bats  d:termine  tbe  existence 
of  the  larger  naturalized  quadrupeds  in  several  parts  of 
South  America. 

We  see  in  many  cases  in  the  more  recent  tertiary  forma¬ 
tions  that  rarity  precedes  extinction;  and  we  know  that 
this  has  been  the  progress  of  events  with  those  animah 
which  have  been  exterminated,  either  locally  or  wholly, 
through  man’s  agency.  I  may  repeat  what  I  published  in 
1845,  namely,  that  to  admit  that  species  generally  become 
rare  before  they  become  extinct — to  feel  no  surprise  at  the 
rarity  of  a  species,  and  yet  to  marvel  greatly  when  the  spe¬ 
cies  ceases  to  exist,  is  much  the  same  as  to  admit  that  sick¬ 
ness  in  the  individual  is  the  forerunner  of  death — to  feel 
no  surprise  at  sickness,  but,  when  the  sick  man  dies,  to 
wonder  and  to  suspect  that  he  died  by  some  deed  of 
violence. 


350 


EXTINCTION. 


The  theory  of  natural  selection  is  grounded  on  the  belief 
that  each  new  variety  and  ultimately  each  new  species,  is 
produced  and  maintained  by  having  some  advantage  over 
those  with  which  it  comes  into  competition;  and  the  con¬ 
sequent  extinction  of  the  less-favored  forms  almost  inevita¬ 
bly  follows.  It  is  the  same  with  our  domestic  productions; 
when  a  new  and  slightly  improved  variety  has  been  raised, 
it  at  first  supplants  the  less  improved  varieties  in  the  same 
neighborhood;  when  much  improved  it  is  transported  far 
and  near,  like  our  sliort-horn  cattle,  and  takes  the  place  of 
other  breeds  in  other  countries.  Thus  the  appearance  of 
new  forms  and  the  disappearance  of  old  forms,  both  those 
naturally  and  those  artificially  produced,  are  bound 
together.  In  flourishing  groups,  the  number  of  new  spe¬ 
cific  forms  which  have  been  produced  within  a  given  time 
has  at  some  periods  probably  been  greater  than  the  number 
of  the  old  specific  forms  which  have  been  exterminated; 
but  we  know  that  species  have  not  gone  on  indefinitely  in¬ 
creasing,  at  least  during  the  later  geological  epochs,  so 
that,  looking  to  later  times,  we  may  believe  that  the  pro¬ 
duction  of  new  forms  has  caused  the  extinction  of  about 
the  same  number  of  old  forms. 

The  competition  will  generally  be  most  severe,  as  for¬ 
merly  explained  and  illustrated  by  examples,  between  the 
forms  which  are  most  like  each  other  in  all  respects.  Hence 
the  improved  and  modified  descendants  of  a  species  will 
generally  cause  the  extermination  of  the  parent-species; 
and  if  many  new  forms  have  been  developed  from  any 
one  species,  the  nearest  allies  of  that  species,  i.  e. 
the  species  of  the  same  genus,  will  be  the  most  liable 
to  extermination.  Thus,  as  I  believe,  a  number  of  new 
species  descended  from  one  species,  that  is  a  new  genus, 
comes  to  supplant  an  old  genus,  belonging  to  the  same 
family.  But  it  must  often  have  happened  that  a  new 
species  belonging  to  some  one  group  has  seized  on  the  place 
occupied  by  a  species  belonging  to  a  distinct  group,  and 
thus  have  caused  its  extermination.  If  many  allied  forms 
be  developed  from  the  successful  intruder,  many  will  have 
to  yield  their  places;  and  it  will  generally  be  the  allied 
forms,  which  will  suffer  from  some  inherited  inferiority  :n 
common.  But  whether  it  be  species  belonging  to  the 
same  or  to  a  distinct  class,  which  have  yielded  their  places 


EXTINCTION. 


351 


to  other  modified  and  improved  species,  a  few  of  the  suf¬ 
ferers  may  often  be  preserved  for  a  long  time,  from  being 
fitted  to  some  peculiar  line  of  life,  or  from  inhabiting  some 
distant  and  isolated  station,  where  they  will  have  escaped 
severe  competition.  For  instance,  some  species  of  Trigo- 
nia,  a  great  genus  of  shells  in  the  secondary  formations, 
survive  in  the  Australian  seas;  and  a  few  members  of  the 
great  and  almost  extinct  group  of  Ganoid  fishes  still  inhabit 
our  fresh  waters.  Therefore,  the  utter  extinction  of  a 
group  is  generally,  as  we  have  seen,  a  slower  process  than 
its  production. 

With  respect  to  the  apparently  sudden  extermination  of 
whole  families  or  orders,  as  of  Trilobites  at  the  close  of  the 
palaeozoic  period,  and  of  Ammonites  at  the  close  of  the 
secondary  period,  we  must  remember  what  has  been  already 
said  on  the  probable  wide  intervals  of  time  between  our 
consecutive  formations;  and  in  these  intervals  there  may 
have  been  much  slow  extermination.  Moreover,  when,  by 
sudden  immigration  or  by  unusually  rapid  development, 
many  species  of  a  new  group  have  taken  possession  of  an 
area,  many  of  the  older  species  will  have  been  exterminated 
in  a  correspondingly  rapid  manner;  and  the  forms  which 
thus  yield  their  places  will  commonly  be  allied,  for  they 
will  partake  of  the  same  inferiority  in  common. 

Thus,  as  it  seems  to  me,  the  manner  in  which  single 
species  and  whole  groups  of  species  become  extinct  accords 
well  with  the  theorv  of  natural  selection.  We  need  not 
marvel  at  extinction;  if  we  must  marvel,  let  it  be  at  our 
own  presumption  in  imagining  for  a  moment  that  we  un¬ 
derstand  the  many  complex  contingencies  on  which  the 
existence  of  each  species  depends.  If  we  forget  for  an 
instant  that  each  species  tends  to  increase  inordinately, 
and  that  some  check  is  always  in  action,  yet  seldom  per¬ 
ceived  by  us,  the  whole  economy  of  nature  will  be  utterly 
obscured.  Whenever  we  can  precisely  say  why  this  species 
is  more  abundant  in  individuals  than  that;  why  this 
species  and  not  another  can  be  naturalized  in  a  given  coun¬ 
try;  then,  and  not  until  then,  we  may  justly  feel  surprise 
why  we  cannot  account  for  the  extintion  of  any  particular 
species  or  group  of  species. 


FORMS  OF  LIFE  CHANGING 


ON  THE  FORMS  OF  LIFE  CHANGING  ALMOST  SIMULTA¬ 
NEOUSLY  THROUGHOUT  THE  WORLD. 

Scarcely  any  pala3ontological  discovery  is  more  striking 
than  the  fact  that  the  forms  of  life  change  almost  simul¬ 
taneously  throughout  the  world.  Thus  our  European 
Chalk  formation  can  be  recognized  in  many  distant  regions, 
under  the  most  different  climates,  where  not  a  frag¬ 
ment  of  the  mineral  chalk  itself  can  be  found;  namely,  in 
North  America,  in  equatorial  South  America,  in  Tierra 
del  Fuego,  at  the  Cape  of  Good  Hope,  and  in  the  peninsula 
of  India.  For  at  these  distant  points,  the  organic  remains 
in  certain  beds  present  an  unmistakable  resemblance  to 
those  of  the  Chalk.  It  is  not  that  the  same  species  are 
met  with;  for  in  some  cases  not  one  species  is  identically 
the  same,  but  they  belong  to  the  same  families,  genera, 
and  sections  of  genera,  and  sometimes  are  similarly  char¬ 
acterized  in  such  trifling  points  as  mere  superficial  sculp¬ 
ture.  Moreover,  other  forms,  which  are  not  found  in  the 
Chalk  of  Europe,  but  which  occur  in  the  formations  either 
above  or  below,  occur  in  the  same  order  at  these  distant 
points  of  the  world.  In  the  several  successive  palaeozoic 
formations  of  Russia,  Western  Europe,  and  North  America, 
a  similar  parallelism  in  the  forms  of  life  has  been  observed 
by  several  authors;  so  it  is,  according  to  Lyell,  with  the 
European  and  North  American  tertiary  deposits.  Even  if 
the  few  fossil  species  which  are  common  to  the  Oid  and 
New  Worlds  were  kept  wholly  out  of  view,  the  general 
parallelism  in  the  successive  forms  of  life,  in  the  palaeozoic 
and  tertiary  stages,  would  still  be  manifest,  and  the  several 
formations  could  be  easily  correlated. 

These  observations,  however,  relate  to  the  marine  inhabi¬ 
tants  of  the  world:  we  have  not  sufficient  data  to  judge 
whether  the  productions  of  the  land  and  of  fresh  water  at 
distant  points  change  in  the  same  parallel  manner.  We 
may. doubt  whether  they  have  thus  changed:  if  the  Mega¬ 
therium,  Mylodon,  Macrauchenia,  and  Toxodon  had  been 
brought  to  Europe  from  La  Plata,  without  any  information 
in  regard  to  their  geological  position,  no  one  would  have 
suspected  that  they  had  co-existed  with  sea-shells  all  still 
living;  but  as  these  anomalous  monsters  co-existed  with 
the  Mastodon  and  Horse,  it  might  at  least  have  been  in- 


THROUGHOUT  THE  WORLD.  353 

ferred  that  they  had  lived  during  one  of  the  later  tertiary 
stages. 

When  the  marine  forms  of  life  are  spoken  of  as  having 
changed  simultaneously  throughout  the  world,  it  must  not 
be  supposed  that  this  expression  relates  to  the  same  year, 
or  to  the  same  century,  or  even  that  it  has  a  very  strict 
geological  sense;  for  if  all  the  marine  animals  now  living 
in  Europe,  and  all  those  that  lived  in  Europe  during  the 
pleistocene  period  (a  very  remote  period  as  measured  by 
years,  including  the  whole  glacial  epoch)  were  compared 
with  those  now  existing  in  South  America  or  in  Australia, 
the  most  skillful  naturalist  would  hardly  be  able  to  say 
whether  the  present  or  the  pleistocene  inhabitants  of 
Europe  resembled  most  closely  those  of  the  southern  hemi¬ 
sphere..  So,  again,  several  highly  competent  observers 
maintain  that  the  existing  productions  of  the  United  States 
are  more  closely  related  to  those  which  lived  in  Europe 
during  certain  late  tertiary  stages,  than  to  the  present  in¬ 
habitants  of  Europe;  and  if  this  be  so,  it  is  evident  that 
fossiliferous  beds  now  deposited  on  the  shores  of  North 
America  would  hereafter  be  liable  to  be  classed  with  some¬ 
what  older  European  beds.  Nevertheless,  looking  to  a 
remotely  future  epoch,  there  can  be  little  doubt  that  all 
the  more  modern  marine  formations,  namely,  the  upper 
pliocene,  the  pleistocene  and  strictly  modern  beds  of 
Europe,  North  and  South  America,  and  Australia,  from 
containing  fossil  remains  in  some  degree  allied,  and  from 
not  including  those  forms  which  are  found  only  in  the 
older  underlying  deposits,  would  be  correctly  ranked  as 
simultaneous  in  a  geological  sense. 

The  fact  of  the  forms  of  life  changing  simultaneously  in 
the  above  large  sense,  at  distant  parts  of  the  world,  has 
greatly  struck  those  admirable  observers,  MM.  de  Verneuil 
and  d'Archiac.  After  referring  to  the  parallelism  of  the 
palaeozoic  forms  of  life  in  various  parts  of  Europe,  they  add, 
“If,  struck  by  this  strange  sequence,  we  turn  our  atten¬ 
tion  to  North  America,  and  there  discover  a  series  of  ana¬ 
logous  phenomena,  it  will  appear  certain  that  all  these 
modifications  of  species,  their  extinction,  and  the  intro¬ 
duction  of  new  ones,  can  not  be  owing  to  mere  changes  in 
marine  currents  or  other  causes  more  or  less  local  and 
temporary,  but  depend  on  general  laws  which  govern  the 


l 


354 


FORMS  OF  LIFE  CUANGING 


whole  animal  kingdom.”  M.  Barrande  has  made  forcible 
remarks  to  precisely  the  same  effect.  It  is,  indeed,  quite 
futile  to  look  to  changes  of  currents,  climate,  or  other  phy¬ 
sical  conditions,  as  the  cause  of  these  great  mutations  in 
the  forms  of  life  throughout  the  world,  under  the  most 
different  climates.  We  must,  as  Barrande  has  remarked, 
look  to  some  special  law.  We  shall  see  this  more  clearly 
when  we  treat  of  the  present  distribution  of  organic  beings, 
and  find  how  slight  is  the  relation  between  the  physical 
conditions  of  various  countries  and  the  nature  of  their 
inhabitants. 

This  great  fact  of  the  parallel  succession  of  the  forms  of 
life  throughout  the  world,  is  explicable  on  the  theory  of 
natural  selection.  New  species  are  formed  by  having  some 
advantage  over  older  forms;  and  the  forms,  which  are 
already  dominant,  or  have  some  advantage  over  the  other 
forms  in  their  own  country,  give  birth  to  the  greatest 
number  of  new  varieties  or  incipient  species.  We  have 
distinct  evidence  on  this  head,  in  the  plants  which  are 
dominant,  that  is,  which  are  commonest  and  most  widely 
diffused,  producing  the  greatest  number  of  new  varieties. 
It  is  also  natural  that  the  dominant,  varying  and  far- 
spreading  species,  which  have  already  invaded,  to  a  certain 
extent,  the  territories  of  other  species,  should  be  those 
which  would  have  the  best  chance  of  spreading  still  further, 
and  of  giving  rise  in  new  countries  to  other  new  varieties 
and  species.  The  process  of  diffusion  would  often  be  very 
slow,  depending  on  climatal  and  geographical  changes,  on 
strange  accidents,  and  on  the  gradual  acclimatization  of 
new  species  to  the  various  climates  through  wdrich  they 
might  have  to  pass,  but  in  the  course  of  time  the  domi¬ 
nant  forms  would  generally  succeed  in  spreading  and  would 
ultimately  prevail.  The  diffusion  would,  it  is  probable,  be 
slower  with  the  terrestrial  inhabitants  of  distinct  conti¬ 
nents  than  with  the  marine  inhabitants  of  the  continuous 
sea.  We  might  therefore  expect  to  find,  as  we  do  find,  a 
less  strict  degree  of  parallelism  in  the  succession  of  the 
productions  of  the  land  than  with  those  of  the  sea. 

Thus,  as  it  seems  to  me,  the  parallel,  and,  taken  in  a 
large  sense,  simultaneous,  succession  of  the  same  forms  of 
life  throughout  the  world,  accords  well  with  the  principle 
of  new  species  having  been  formed  by  dominant  species 


THROUGHOUT  THE  WORLD. 


355 


spreading  widely  and  varying;  the  new  species  thus  pro¬ 
duced  being  themselves  dominant,  owing  to  their  having 
had  some  advantage  over  their  already  dominant  parents, 
as  well  as  over  other  species,  and  again  spreading,  varying, 
and  producing  new  forms.  The  old  forms  which  are 
beaten  and  which  yield  their  places  to  the  new  and  victori¬ 
ous  forms,  will  generally  be  allied  in  groups,  from  inherit¬ 
ing  some  inferiority  in  common;  and,  therefore,  as  new 
and  improved  groups  spread  throughout  the  world,  old 
groups  disappear  from  the  world;  and  the  succession  of 
forms  everywhere  tends  to  correspond  both  in  their  first 
appearance  and  final  disappearance. 

There  is  one  other  remark  connected  with  this  subject 
worth  making.  I  have  given  my  reasons  for  believing 
that  most  of  our  great  formations,  rich  in  fossils,  were 
deposited  during  periods  of  subsidence;  and  that  blank 
intervals  of  vast  duration,  as  far  as  fossils  are  concerned, 
occurred  during  the  periods  when  the  bed  of  the  sea  was 
either  stationary  or  rising,  and  likewise  when  sediment 
was  not  thrown  down  quickly  enough  to  imbed  and  pre¬ 
serve  organic  remains.  During  these  long  and  blank  inter¬ 
vals  I  suppose  that  the  inhabitants  of  each  region 
underwent  a  considerable  amount  of  modification  and 
extinction,  and  that  there  was  much  migration  from  other 
parts  of  the  world.  As  we  have  reason  to  believe  that  large 
areas  are  affected  by  the  same  movement,  it  is  probable 
that  strictly  contemporaneous  formations  have  often  been 
accumulated  over  very  wide  spaces  in  the  same  quarter 
of  the  world ;  but  we  are  very  far  from  having  any 
right  to  conclude  that  this  has  invariably  been  the  case, 
and  that  large  areas  have  invariably  been  affected  by  the 
same  movements.  When  two  formations  have  been  depos¬ 
ited  in  two  regions  during  nearly,  but  not  exactly,  the 
same  _  period,  we  should  find  in  both,  from  the  causes 
explained  in  the  foregoing  paragraphs,  the  same  general 
succession  in  the  forms  of  life  ;  but  the  species  would  not 
exactly  correspond  ;  for  there  will  have  been  a  little  more 
time  in  the  one  region  than  in  the  other  for  modification, 
extinction  and  immigration. 

I  suspect  that  cases  of  this  nature  occur  in  Europe. 
Mr.  Prestwich,  in  his  admirable  Memoirs  on  the  eocene 
deposits  of  England  and  France,  is  able  to  draw  a  close 


356 


AFFINITIES  OF  EXTINCT  SPECIES. 


general  parallelism  between  the  successive  stages  in  the 
two  countries;  but  when  he  compares  certain  stages  in 
England  with  those  in  France,  although  he  finds  in  both  a 
curious  accordance  in  the  numbers  of  the  species  belonging 
to  the  same  genera,  yet  the  species  themselves  differ  in  a 
manner  very  difficult  to  account  for  considering  the  prox¬ 
imity  of  the  two  areas,  unless,  indeed,  it  be  assumed  that 
an  isthmus  separated  two  seas  inhabited  by  distinct,  but 
contemporaneous  faunas.  Lyell  has  made  similar  obser¬ 
vations  on  some  of  the  later  tertiary  formations.  Barrande, 
also,  shows  that  there  is  a  striking  general  parallelism  in  the 
successive  Silurian  deposits  of  Bohemia  and  Scandinavia ; 
nevertheless  he  finds  a  suprising  amount  of  difference 
in  the  species.  If  the  several  formations  in  these  regions 
have  not  been  deposited  during  the  same  exact  periods 
—a  formation  in  one  region  often  corresponding  with  a 
blank  interval  in  the  other— and  if  in  both  regions  the 
species  have  gone  on  slowly  changing  during  the  accumu¬ 
lation  of  the  several  formations  and  during  the  long  inter¬ 
vals  of  time  between  them ;  in  this  case  the  several 
formations  in  the  two  regions  could  be  arranged  in  the 
same  order,  in  accordance  with  the  general  succession  of 
the  forms  of  life,  and  the  order  would  falsely  appear  to  be 
strictly  parallel ;  nevertheless  the  species  would  not  be 
all  the  same  in  the  apparently  corresponding  stages  in  the 
two  regions. 

ON  THE  AFFINITIES  OF  EXTINCT  SPECIES  TO  EACH  OTHER, 

AND  TO  LIVING  FORMS. 

Let  us  now  look  to  the  mutual  affinities  of  extinct  and 
living  species.  All  fall  into  a  few  grand  classes  ;  and  thia 
fact  is  at  once  explained  on  the  principle  of  descent. 
The  more  ancient  any  form  is,  the  more,  as  a  general 
rule,  it  differs  from  living  forms.  But,  as  Buckland  long 
ago  remarked,  extinct  species  can  all  be  classed  either  in 
still  existing  groups,  or  between  them.  That  the  extinct 
forms  of  life  help  to  fill  up  the  intervals  between  existing 
genera,  families  and  orders,  is  certainly  true;  but  as  this 
statement  has  often  been  ignored  or  even  denied,  it  may 
be  well  to  make  some  remarks  on  this  subject,  and  to  give 
some  instances,  If  we  confine  our  attention  either  to  the 


AFFINITIES  OF  EXTINCT  SPECIES.  357 

living  or  to  the  extinct  species  of  the  same  class,  the  series 
is  fai  less  perfect  than  if  we  combine  both  into  one  general 
system..  In  the  writings  of  Professor  Owen  we  continually 
meet  with  the  expression  of  generalized  forms,  as  applied 
to  extinct  animals;  and  in  the  writings  of  Agassiz,  of 
prophetic  or  synthetic  types;  and  these  terms  imply  that 
such  forms  are,  in  fact,  intermediate  or  connecting  links 
Another  distinguished  palaeontologist,  M.  Gaudry,  has 
shown  in  the  most  striking  manner  that  many  of  the  fossil 
mammals  diseo\ered  by  him  in  Attica  serve  to  break  down 
the  intervals  between  existing  genera.  Cuvier  ranked  the 
Kummants  and  Pachyderms  as  two  of  the  most  distinct 
orders  of  mammals;  but  so  many  fossil  links  have  been  dis¬ 
entombed  that  Owen  has  had  to  alter  the  whole  classifica¬ 
tion,  and  has  placed  certain  Pachyderms  in  the  same 
sub-order  with  ruminants;  for  example,  he  dissolves  by 
gradations  the  apparently  wide  interval  between  the  pig 
and  the.  camel.  The  ITngulata  or  hoofed  quadrupeds  are 
now  divided  into  the  even-toed  or  odd-toed  divisions;  but 
the  Maciauchenia  of  South  America  connects  to  a  certain 
extent  these  two  grand  divisions.  No  one  will  deny  that 
the  Hipparion  is  intermediate  between  the  existing  horse 
and  certain  other  ungulate  forms.  What  a  wonderful  con¬ 
necting  link  in  the  chain  of  mammals  is  the  Xypotherium 
from  South  Ameiica,  as  the  name  given  to  it  by  Professor 
Ge.rvais  expresses,  and  which  cannot  be  placed  in  any  ex¬ 
isting  order.  The  Sirenia  form  a  very  distinct  group  of  the 
mammals,  and  one  of  the  most  remarkable  peculiarities  in 
existing  dugong  and  lamentin  is  the  entire  absence  of  hind 
lrmbs,  without  even  a  rudiment  being  left;  but  the  extinct 
Halitherium  had.,  according  to  Professor  Plower,  an  ossified 
\ tnigh-bo.ne^  articulated  to  a  well-defined  acetabulum  in 
the  pelvis,  and  it  thus  makes  some  approach  to  ordinary 
hoofed  quadrupeds,  to  which  the  Sirenia  are  in  other  re¬ 
spects  allied.  The  cetaceans  or  whales  are  widely  different 
from  all  other  mammals,  but  the  tertiary  Zeugiodon  and 
Squalodon,  which  have  been  placed  by  some  naturalists  in 
an  order  by  themselves,  are  considered  by  Professor  Huxley 
to  be  undoubtedly  cetaceans,  “and  to  constitute  connect¬ 
ing  links  with  the  aquatic  carnivora/* 

Even  the  wide  interval  between  birds  arid  reptiles  has 
been  shown  by  the  naturalist  [just  quoted  to  bC  martially 


S58 


AFFINITIES  OF  EXTINCT  SPECIE 8. 


bridged  over  in  the  most  unexpected  manner,  on  the  one 
hand,  by  the  ostrich  and  extinct  Archeopteryx,  and  on  the 
other  hand  by  the  Compsognathus,  one  of  the  Dinosaurians 
-that  group  which  includes  the  most  gigantic  of  all  ter¬ 
restrial  reptiles.  Turning  to  the  Invertebrata,  Barrande 
asserts,  a  higher  authority  could  not  be  named,  that  he  is 
every  day  taught  that,  although  palaeozoic  animals  can  cer¬ 
tainly  be  classed  under  existing  groups,  yet  that  at  this 
ancient  period  the  groups  were  not  so  distinctly  separated 
from  each  other  as  they  now  are. 

Some  writers  have  objected  to  any  extinct  species,  or 
group  of  species,  being  considered  as  intermediate  between 
any  two  living  species,  or  groups  of  species.  If  by  this 
term  it  is  meant  that  an  extinct  form  is  directly  interme¬ 
diate  in  all  its  characters  between  two  living  forms  or 
groups,  the  objection  is  probably  valid.  But  in  a  natural 
classification  many  fossil  species  certainly  stand  between 
living  species,  and  some  extinct  genera  between  living 
genera,  even  between  genera  belonging  to  distinct  families. 
The  most  common  case,  especially  with  respect  to  very  dis¬ 
tinct  groups,  such  as  fish  and  reptiles,  seems  to  be  that, 
supposing  them  to  be  distinguished  at  the  present  day  by  a 
score  of  characters,  the  ancient  members  are  separated  by  a 
somewhat  lesser  number  of  characters,  so  that  the  two 
groups  formerly  made  a  somewhat  nearer  approach  to  each 
other  than  they  now  do. 

It  is  a  common  belief  that  the  more  ancient  a  form  is,  by 
so  much  the  more  it  tends  to  connect  by  some  of  its  char¬ 
acters  groups  now  widely  separated  from  each  other.  This 
remark  no  doubt  must  be  restricted  to  those  groups  which  ; 
have  undergone  much  change  in  the  course  of  geological 
ages;  and  it  would  be  difficult  to  prove  the  truth  of  the 
proposition,  for  every  now  and  then  even  a  living  animal, 
as  the  Lepidosiren,  is  discovered  having  affinities  directed 
toward  very  distinct  groups.  Yet  if  we  compare  the  older 
reptiles  and  Batrachians,  the  older  fish,  the  older  cephalo- 
pods,  and  the  eocene  mammals,  with  the  recent  members 
of  the  same  classes,  we  must  admit  that  there  is  truth  in 
the  remark. 

Let  us  see  how  far  these  several  facts  and  inferences 
accord  with  the  theory  of  descent  with  modification.  As 
the  subject  is  somewhat  complex,  I  must  request  the  reader 


AFFINITIES  OF  EXTINCT  SPECIES.  339 

to  turn  to  the  diagram  in  the  fourth  chapter.  We  may 
suppose  that  the  numbered  letters  in  italics  represent 
genera,  and  the  dotted  lines  diverging  from  them  the  spe¬ 
cies  in  each  genus.  The  diagram  is  much  too  simple,  too 
few  genera  and  too  few  species  being  given,  but  this  is  un¬ 
important  for  .us.  The  horizontal  lines  may  represent  suc¬ 
cessive  geological  formations,  and  all  the  forms  beneath 
the  uppermost  line  may  be  considered  as  extinct.  The 
three  existing  genera  a1*,  q p44,  will  form  a  small 
family ;  b44  and  fx  4,  a  closely  allied  family  or  subfamily, 
and  tA 4>  e44,  m14,  a  third  family.  These  three  families, 
together  with  the  many  extinct  genera  on  the  several  lines 
of  descent  diverging  from  the  parent  form  (A)  will  form 
an  order,  for  all  will  have  inherited  something  in  common 
from  their  ancient  progenitor.  On  the  principle  of  the 
continued  tendency  to  divergence  of  character,  which  was 
foimerly  illustrated  by  this  diagram,  the  more  recent  any 
form  is  the  more  it  will  generally  differ  from  its  ancient 
progenitor.  Hence,  we  can  understand  the  rule  that  the 
most  ancient  fossils  differ  most  from  existing  forms.  We 
must  not,  however,  assume  that  divergence  of  character  is 
a  necessary  contingency;  it  depends  solely  on  the  descend¬ 
ants  fiom  a  species  being  thus  enabled  to  seize  on  many 
and  different  places  in  the  economy  of  nature.  Therefore 
it  is  .quite  possible,  as  we  have  seen  in  the  case  of  some 
feu u nan  forms,  that  a  species  might  go  on  being  slightly 
modified  in  relation  to  its  slightly  altered  conditions  of 
life,  and  yet  retain  throughout  a  vast  period  the  same  gen- 
eial  chaiacteiistics.  This  is  represented  in  the  diagram  by 
the  letter  f14.  J 

All  the  many  forms,  extinct  and  recent,  descended 
from  (A),  make,  as  before  remarked,  one  order;  and  this 
order,  from  the  continued  effects  of  extinction  and  divero-- 
ence  of  character,  has  become  divided  into  several  sub¬ 
families  and  families,  some  of  which  are  supposed  to  have 
perished  at  different  periods,  and  some  to  have  endured  to 
the  present  day. 

By  looking  at  the  diagram  we  can  see  that  if  many  of 
the  extinct  forms  supposed  to  be  imbedded  in  the  successive 
formations,  were  discovered  at  several  points  low  down  in 
the  seiies,  the  three  existing  families  on  the  uppermost 
line  would  be  rendered  less  distinct  from  each  other.  If, 


360 


AFFINITIES  OF  EXTINCT  SPECIES. 


for  instance,  the  genera  a1,  (P,  a10,  /*,  in*,  m*,  in9,  were  dis¬ 
interred,  these  three  families  would  be  so  closely  linked 
together  that  they  probably  would  have  to  be  united  into 
one  great  family,  in  nearly  the  same  manner  as  has  occurred 
with  ruminants  and  certain  pachyderms.  Yet  he  who 
objected  to  consider  as  intermediate  the  extinct  genera, 
which  thus  link  together  the  living  genera  of  three  fami¬ 
lies,  would  be  partly  justified,  for  they  are  intermediate, 
not  directly,  but  only  by  a  long  and  circuitous  course 
through  many  widely  different  forms.  If  many  extinct 
forms  were  to  be  discovered  above  one  of  the  middle  hori¬ 
zontal  lines  or  geological  formations — for  instance,  above 
No.  VI. — but  none  from  beneath  this  line,  then  only  two 
of  the  families  (those  on  the  left  hand,  au,  etc.,  and  bli, 
etc.)  would  have  to  be  united  into  one;  and  there  would 
remain  two  families,  which  would  be  less  distinct  from 
each  other  than  they  were  before  the  discovery  of  the 
fossils.  So  again,  if  the  three  families  formed  of  eight 
genera  (ali  to  inu),  on  the  uppermost  line,  be  supposed  to 
differ  from  each  other  by  half-a-dozen  important  char¬ 
acters,  then  the  families  which  existed  at  a  period  marked 
VI  would  certainly  have  differed  from  each  other  by  a  less 
number  of  characters;  for  they  would  at  this  early  stage  of 
descent  have  diverged  in  a  less  degree  from  their  common 
progenitor.  Thus  it  comes  that  ancient  and  extinct 
genera  are  often  in  a  greater  or  less  degree  intermediate  in 
character  between  their  modified  descendants,  or  between 
their  collateral  relations. 

Under  nature  the  process  will  be  far  more  complicated 
than  is  represented  in  the  diagram;  for  the  groups  will 
have  been  more  numerous;  they  will  have  endured  for 
extremely  unequal  lengths  of  time,  and  will  have  been 
modified  in  various  degrees.  As  we  possess  only  the  last 
volume  of  the  geological  record,  and  that  in  a  very  broken 
condition,  we  have  no  right  to  expect,  except  in  rare  cases, 
to  fill  up  the  wide  intervals  in  the  natural  system,  and 
thus  to  unite  distinct  families  or  orders.  All  that  we  have 
a  right  to  expect  is,  that  those  groups  which  have,  within 
known  geological  periods,  undergone  much  modification, 
should  in  the  older  formations  make  some  slight  approach 
to  each  other;  so  that  the  older  members  should  differ  less 
from  each  other  in  some  of  their  characters  than  do  the 


AFFINITIES  OF  ESTINC1  SPECIES.  gg. 

I  -  i  •  -J  _  same  groups;  and  this  by  the 

concurrent  evidence  of  our  best  palaeontologists  is  fre¬ 
quently  the  case.  6 

Thus,  on  the  theory  of  descent  with  modification,  the 
mam  facts  with  respeot  to  the  mutual  affinities  of  the 
extinct  forms  of  life  to  each  other  and  to  living'  forms 
are  explained  in  a  satisfactory  manner.  And  they  are 
wholly  inexplicable  on  any  other  view. 

On  this  same  theory,  itis  evident  that  thefaunadurineany 
one  great  period  in  the  earth’s  history  will  be  intermediate 
in  general  character  between  that  which  preceded  and 
that  which  succeeded  it.  Thus  the  species  which  lived 
at  the  sixth  great  stage  of  descent  in  the  diagram  are  the 
modified  offspring  of  those  which  lived  at  the  fifth  stage 
and  are  the  parents  of  those  which  became  still  more 
modified  at  the  seventh  stage;  hence  they  could  hardly  fail 
to  be  nearly  intermediate  in  character  between  the  forms 
of  life  above  and  below.  We  must,  however,  allow  for  the 
entire  extinction  of  some  preceding  forms,  and  in  any  one 
region  for  the  immigration  of  new  forms  from  other 
legions,  and  for  a  large  amount  of  modification  during  the 
long  and  blank  intervals  between  the  successive  formations 
Subject  to  these  allowances,  the  fauna  of  each  geological 
penod  undoubtedly  is  intermediate  in  character,  between 
the  preceding  and  succeeding  faunas.  I  need  give  only 
one  instance,  namely,  the  manner  in  which  the  fossils  of  the 
Devonian  system,  when  this  system  was  first  discovered 
were  at  once  recognized  by  paleontologists  as  intermediate 
m  character  between  those  of  the  overlying  carboniferous 
and  underlying  Silurian  systems.  But  each  fauna  is  not 
necessarily  exactly  intermediate,  as  unequal  intervals  of 
time  have  elapsed  between  consecutive  formations 
it  is  no  real  objection  to  the  truth  of  the  statement  that 
the  fauna  of  each  period  as  a  whole  is  nearly  intermediate 
m  character  between  the  preceding  and  succeeding  faunas, 
that  certain  genera  offer  exceptions  to  the  rule.  For  instance, 
the  species  of  mastodons  and  elephants,  when  arranged  by 
f?r*.  falconer  in  two  series-in  the  first  place  according  to 
then  mutual  affinities,  and  in  the  second  place  according  to 
their  periods  of  existence— do  not  accord  in  arrangement, 
lhe  species  extreme  in  character  are  not  the  oldest  or  the 
aiost  recent;  nor  are  those  which  are  intermediate  in  char- 


363  AFFINITIES  OF  EXTINCT  SPECIES. 

acter,  intermediate  in  age.  But  supposing  for  an  instant,  in 
this  and  other  such  cases,  that  the  record  of  the  first  appear¬ 
ance  and  disappearance  of  the  species  was  complete,  which 
is  far  from  the  case,  we  have  no  reason  to  believe  that  forms 
successively  produced  necessarily  endure  for  corresponding 
lengths  of  time.  A  very  ancient  form  may  occasionally  have 
lasted  much  longer  than  a  form  elsewhere  subsequently 
produced,  especially  in  the  case  of  terrestrial  productions 
inhabiting  separated  districts.  To  compare  small  things 
with  great;  if  the  principle  living  and  extinct  races  of  the 
domestic  pigeon  were  arranged  in  serial  affinity,  this  ar¬ 
rangement  would  not  closely  accord  with  the  order  in  time 
of  their  production,  and  even  less  with  the  order  of  tlieir 
disappearance;  for  the  parent  rock-pigeon  still  lives;  and 
many  varieties  between  the  rock-pigeon  and  the  carriei 
have  become  extinct;  and  carriers  which  are  extreme  in 
the  important  character  of  length  of  beak  originated  earlier 
than  short-beaked  tumblers,  which  are  at  the  opposite  end 
of  the  series  in  this  respect. 

Closely  connected  with  the  statement,  that  the  organic 
remains  "from  an  intermediate  formation  are  in  some  degiee 
intermediate  in  character,  is  the  fact,  insisted  on  by  all 
paleontologists,  that  fossils  from  two  consecutive  forma¬ 
tions  are  far  more  closely  related  to  each  other,  than  are 
the  fossils  from  two  remote  formations.  Pictet  gives  as 
a  well-known  instance,  the  general  resemblance  of  the 
organic  remains  from  the  several  stages  of  the  Chalk 
formation,  though  the  species  are  distinct  in  each  stage. 
This  fact  alone,  from  its  .  generality,  seems  to  have 
shaken  Professor  Pictet  in  his  belief  in  the  immutability 
of  species.  He  who  is  acquainted  with  the  distribution 
of  existing  species  over  the  globe,  will  not  attempt  to 
account  for  the  close  resemblance  of  distinct  species  in 
closely  consecutive  formations,  by  the  physical  conditions 
of  the  ancient  areas  having  remained  nearly  the  same. 
Let  it  be  remembered  that  the  forms  of  life,  at  least  those 
inhabiting  the  sea,  have  changed  almost  simultaneously 
throughout  the  world,  and  therefore  under  the  most 
different  climates  and  conditions.  Consider  the  prodig¬ 
ious  viscisitudes  of  climate  during  the  pleistocene  period, 
which  includes  the  whole  glacial  epoch,  and  note  how 
little  the  specific  forms  of  the  inhabitants  of  the  sea  have 
been  affected. 


AFFINITIES  OF  EXTINCT  SPECIES.  363 

On  the  theory  of  descent,  the  full  meaning  of  the  fossil 
remains  from  closely  consecutive  formations  being  closely 
related,  though  ranked  as  distinct  species,  is  obvious.  As 
the  accumulation  of  each  formation  has  often  been  inter¬ 
rupted,  and  as  long  blank  intervals  have  intervened 
between  successive  formations,  we  ought  not  to  expect  to 
find,  as  I  attempted  to  show  in  the  last  chapter,  in  anv  one 
or  in  any  two  formations,  all  the  intermediate  varieties 
between  the  species  which  appeared  at  the  commencement 
and  close  of  these  periods:  but  we  ought  to  find  after 
intervals,  very  long  as  measured  by  years,  but  only  moder¬ 
ately  long  as  measured  geologically,  closely  allied  forms, 
or,  as  they  have  been  called  by  some  authors,  representa¬ 
tive  species;  and  these  assuredly  we  do  find.  We  find,  in 
short, .  such  evidence  of  the  slow  and  scarcely  sensible 
mutations  of  specific  forms,  as  we  have  the  right  to 
expect. 

Otf  THE  STATE  OF  DEVELOPMENT  OF  ANCIENT  COMPARED 

WITH  LIVING  FORMS. 

We  have  seen  in  the  fourth  chapter  that  the  degree  of 
differentiation  and  specialization  of  the  parts  in  organic 
beings,  when  arrived  at  maturity,  is  the  best  standard,  as 
yet  suggested,  of  their  degree  of  perfection  or  highness. 
We  have  also  seen  that,  as  the  specialization  of  parts  is  an 
advantage  to  each  being,  so  natural  selection  will  tend  to 
render  the  organization  of  each  being  more  specialized  and 
perfect,  and  in  this  sense  higher;  not  but  that  it  may  leave 
many  creatures  with  simple  and  unimproved  structures 
fitted  for  simple  conditions  of  life,  and  in  some  cases  will 
even  degrade  or  simplify  the  organization,  yet  leaving 
such  degraded  beings  better  fitted  for  their  new  walks  of 
life.  In  another  and  more  general  manner,  new  species 
become  superior  to  their  predecessors;  for  they  have  to 
beat  in  the.  struggle  for  life  all  the  older  forms,  with  which 
they  come  into  close  competition.  We  may  therefore  con¬ 
clude  that  if  under  a  nearly  similar  climate  the  eocene 
inhabitants  of  the  world  could  be  put  into  competition 
with  the  existing  inhabitants,  the  former  would  be  beaten 
and  exterminated  by  the  latter,  as  would  the  secondary  by 
the  eocene,  and  the  palaeozoic  by  the  secondary  forms.  So 


ae4 


STATE  OF  DEVELOPMENT  OF 


that  by  this  fundamental  test  of  victory  in  the  battle  for 
life,  as  well  as  by  the  standard  of  the  specialization  of 
organs,  modern  forms  ought,  on  the  theory  of  natural 
selection,  to  stand  higher  than  ancient  forms.  Is  this 
the  case?  A  large  majority  of  palaeontologists  would 
answer  in  the  affirmative;  and  it  seems  that  this  answer 
must  be  admitted  as  true,  though  difficult  of  proof. 

It  is  no  valid  objection  to  this  conclusion,  that  certain 
Brachiopods  have  been  but  slightly  modified  from  an 
extremely  remote  geological  epoch;  and  that  certain  land 
and  fresh-water  shells  have  remained  nearly  the  same,  from 
the  time  when,  as  far  as  is  known,  they  first  appeared. 
It  is  not  an  insuperable  difficulty  that  Foraminifera 
have  not,  as  insisted  on  by  Dr.  Carpenter,  progressed  in 
organization  since  even  the  Laurentian  epoch;  for  some 
organisms  would  have  to  remain  fitted  for  simple  condi¬ 
tions  of  life,  and  what  could  be  better  fitted  for  this  end 
than  these  lowly  organized  Protozoa?  Such  objections  as 
the  above  would  be  fatal  to  my  view,  if  it  included  advance 
in  organization  as  a  necessary  contingent.  They  would 
likewise  be  fatal,  if  the  above  Foraminifera,  for  instance, 
could  be  proved  to  have  first  come  into  existence  during 
the  Laurentian  epoch,  or  the  above  Brachiopods  during  the 
Cambrian  formation;  for  in  this  case,  there  would  not  have 
been  time  sufficient  for  the  development  of  these  organ¬ 
isms  up  to  the  standard  which  they  had  then  reached. 
When  advanced  up  to  any  given  point,  there  is  no  neces¬ 
sity,  on  the  theory  of  natural  selection,  for  their  further 
continued  process;  though  they  will,  during  each  succes¬ 
sive  age,  have  to  be  slightly  modified,  so  as  to  hold  their 
places  in  relation  to  slight  changes  in  their  conditions. 
The  foregoing  objections  hinge  on  the  question  whether  we 
really  know  how  old  the  world  is,  and  at  what  period  the 
various  forms  of  life  first  appeared;  and  this  may  well  be 
disputed. 

The  problem  whether  organization  on  the  whole  has 
advanced  is  in  many  ways  excessively  intricate.  The  geo¬ 
logical  record,  at  all  times  imperfect,  does  not  extend  far 
enough  back  to  show  with  unmistakable  clearness  that 
wikhin  the  known  history  of  the  world  organization  has 
largely  advanced.  Even  at  the  present  day,  looking  to 
members  of  the  same  class,  naturalists  are  not  unanimous 


ANCIENT  AND  LIVING  NORMS. 


305 


wtCh  ff°/.mS  °,Ught  t0  be  ranked  as  h'ghest:  thus,  some 
look  at  the  selaceans  or  sharks,  from  their  approach  in 

some  important  points  of  structure  to  reptiles,  as  the  high¬ 
est  fish;  others  look  at  the  teleosteans  as 'the  highest.  The 
ganoids  stand  intermediate  between  the  selaceans  and 
teleosteans;  tne  latter  at  the  present  day  are  largely  pre¬ 
ponderant  in  number;  but  formerly  selaceans  and  ganoids 
alone  existed;  and  m  this  case,  according  to  the  standard 
of  highness  chosen,  so  will  it  be  said  that  fishes  have 
advanced  or  retrograded  in  organization.  To  attempt  to 
compare  members  of  distinct  types  in  the  scale  of  highness 
seems  hopeless;  who  will  decide  whether  a  cuttle-fish  be 
higher  than  a  bee— that  insect  which  the  great  Von  Baer 
believed  to  be  ‘  m  fact  more  highly  organized  than  a  fish, 
although  upon  another  type?”  In  the  complex  struggle 
foi  life  it  is  quite  credible  that  crustaceans,  not  very  high 
in  their  own  class,  might  beat  cephalopods,  the  highest 
mollucs;  and  such  crustaceans,  though  not  highly  devel¬ 
oped,  would  stand  very  high  in  the  scale  of  invertebrate 
animals  if  judged  by  the  most  decisive  of  all  trials— the 
law  ot  battle.  Beside  these  inherent  difficulties  in  decid¬ 
ing  which  forms  are  the  most  advanced  in  organization, 
we  ought  not  solely  to  compare  the  highest  members  of  a 
class  at  any  two  periods— though  undoubtedly  this  is  one 
and  perhaps  the  most  important  element  in  striking  a  bal¬ 
ance— but  we  ought  to  compare  all  the  members,  high  and 
low,  at  two  periods.  At  an  ancientepoch  the  highest  and  low¬ 
est  molluscoidal  animals,  namely,  cephalopods  and  brachio- 
pods,  swarmed  m  numbers;  at  the  present  time  both  groups 
are  greatly  reduced  while  others,  intermediate  in  organi¬ 
zation,  have  largely  increased;  consequently  some  natu¬ 
ralists  maintain  that  molluscs  were  formerly  more  highly 
developed  than  at  present;  but  a  stronger  case  can  be  made 
out  on  the  opposite  side,  by  considering  the  vast  reduction 
bi achiopods,  and  the  fact  that  our  existing  cephalopods, 
though  few  in  number,  are  more  highly  organized  than 
their  ancient  representatives.  We  ought  also  to  compare 
ie  lelative  proportional  numbers,  at  any  two  periods,  of 
the  high  and  low  classes  throughout  the  world:  if  for 
instance,  at  the  present  day  fifty  thousand  kinds  of  verte¬ 
brate  animals  exist,  and  if  we  knew  that  at  some  former 
period  only  ten  thousand  kinds  existed,  we  ought  to  look 


366  STATE  OF  DEVELOPMENT  OF 

at  this  increase  in  number  in  the  highest  class,  which  im¬ 
plies  a  great  displacement  of  lower  forms,  as^  a  decided 
advance  in  the  organization  of  the  world.  W  e  thus  see 
how  hopelessly  difficult  it  is  to  compare  with  peifect  faii- 
ness,  under  such  extremely  complex  relations,  the  standaid 
of  organization  of  the  imperfectly- known  faunas  of  succes¬ 
sive  periods.  -,,111 

We  shall  appreciate  this  difficulty  more  clearly  by  look¬ 
ing  to  certain  existing  faunas  and  floras.  From  the  extra¬ 
ordinary  manner  in  which  European  productions  have 
recently  spread  over  New  Zealand,  and  have  seized  on 
places  which  must  have  been  previously  occupied  by  the 
indigenes,  we  must  believe,  that  if  all  the  animals  and 
plants  of  Great  Britain  were  set  free  in  New  Zealand,  a 
multitude  of  British  forms  would  in  the  course  of  time 
become  thoroughly  naturalized  there,  and  would  exter¬ 
minate  many  of  the  natives.  On  the  other  hand,  from  the 
fact  that  hardly  a  single  inhabitant  of  the  southern  hemi¬ 
sphere  has  become  wild  in  any  part  of  Europe,  we  may 
well  doubt  whether,  if  all  the  productions  of  New  Zealand 
were  set  free  in  Great  Britain,  any  consideiable  number 
would  be  enabled  to  seize  on  places  now  occupied  by  our 
native  plants  and  animals.  Under  this  point  of  view,  the 
productions  of  Great  Britain  stand  much  higher  in  the 
scale  than  those  of  New  Zealand.  Yet  the  most  skillful 
naturalist,  from  an  examination  of  the  species  of  tne  two 
countries,  could  not  have  foreseen  this  result. 

Agassiz  and  several  other  highly  competent  judges  insist 
that  ancient  animals  resemble  to  a  certain  extent  the  em¬ 
bryos  of  recent  animals  belonging  to  the  same  classes;  and 
that  the  geological  succession  of  extinct  forms  is  nearly 
parallel  with  the  embryological  development  of  existing 
forms.  This  view  accords  admirably  well  with  our  theory. 
In  a  future  chapter  I  shall  attempt  to  show  that  the  adult 
differs  from  its  embryo,  owing  to  variations  having  super¬ 
vened  at  a  not  early  age,  and  having  been  inherited  at  a 
corresponding  age.  This  process,  while  it  leaves  the  em¬ 
bryo  almost  unaltered,  continually  adds,  in  the  course  of 
successive  generations,  more  and  more  difference  to  the 
adult.  Thus  the  embryo  comes  to  be  left  as  a  sort  of 
picture,  preserved  by  nature,  of  the  former  and  less  modi¬ 
fied  condition  of  the  species.  This  view  may  be  true,  and 


ANCIENT  AND  LIVING  FORMS 


367 

may  never  be  capable  of  proof.  Seeing,  for  instance, 
that  the  oldest  known  mammals,  reptiles,  and  fishes  strictly 
belong  to  their  proper  classes,  though  some  of  these  old 
forms  are  in  a  slight  degree  less  distinct  from  each  other 
than  are  the  typical  members  of  the  same  groups  at  the 
present  day,  it  would  be  vain  to  look  for  animals  having 
the  common  embryological  character  of  the  vertebrata, 
until  beds  rich  in  fossils  are  discovered  far  beneath  the 
lowest  Cambrian  strata — a  discovery  of  which  the  chance 
is  small. 

(W  THE  SUCCESSION  OF  THE  SAME  TYPES  WITHIN  THE 
THE  SAME  AREAS,  DURING  THE  LATER  TERTIARY 
PERIODS. 

Mr.  Clift  many  years  ago  showed  that  the  fossil  mam¬ 
mals  from  the  Australian  caves  were  closely  allied  to  the 
living  marsupials  of  that  continent.  In  South  America,  a 
similar  relationship  is  manifest,  even  to  an  uneducated 
eye,  in  the  gigantic  pieces  of  armor,  like  those  of  the  arma¬ 
dillo,  found  in  several  parts  of  La  Plata;  and  Professor 
Owen  has  shown  in  the  most  striking  manner  that  most  of 
the  fossil  mammals,  buried  there  in  such  numbers,  are  re¬ 
lated  to  South  American  types.  This  relationship  is  even 
more  clearly  seen  in  the  wonderful  collection  of  fossil  bones 
made  by  MM.  Lund  and  Clausen  in  the  caves  of  Brazil.  I 
was  so  much  impressed  with  these  facts  that  I  stronglv  in¬ 
sisted,  in  1839  and  1845,  on  this  “law  of  the  succession  of 
types/— on  “this  wonderful  relationship  in  the  same  con¬ 
tinent  between  the  dead  and  the  living.”  Professor  Owen 
has  subsequently  extended  the  same  generalization  to  the 
mammals  of  the  Old  World.  We  see  the  same  law  in  this 
author’s  restorations  of  the  extinct  and  gigantic  birds  of 
New. Zealand.  We  see  it  also  in  the  birds  of  the  caves  of 
Brazil.  .  Mr.  Woodward  has  shown  that  the  same  law  holds 
good  with  sea-shells,  but,  from  the  wide  distribution  of 
most  molluscs,  it  is  not  well  displayed  by  them.  Other 
cases  could  be  added,  as  the  relation  between  the  extinct 
and  living  land-shells  of  Madeira;  and  between  the  extinct 
and^  living  brackish  water-shells  of  the  Aralo-Caspian  Sea. 

Now,  what  does  this  remarkable  law  of  the  succession  of 
the  same  types  within  the  same  areas  mean?  He  would  be  a 


368 


SUCCESSION  OF  THE 


bold  man  who,  after  comparing  the  present  climate  of 
Australia  and  of  parts  of  South  America,  under  the  same 
latitude,  would  attempt  to  account,  on  the  one  hand 
through  dissimilar  physical  conditions,  for  the  dissimilarity 
of  the  inhabitants  of  these  two  continents  ;  and,  on  the 
other  hand  through  similarity  of  conditions,  for  the  uni¬ 
formity  of  the  same  types  in  each  continent  during  the 
later  tertiary  periods.  Nor  can  it  be  pretended  that  it  is 
an  immutable  law  that  marsupials  should  have  been  chiefly 
or  solely  produced  in  Australia  ;  or  that  Edentata  and 
other  American  types  should  have  been  solely  produced  in 
South  America.  For  we  know  that  Europe  in  ancient 
times  was  peopled  by  numerous  marsupials  ;  and  I  have 
shown  in  the  publications  above  alluded  to,  that  in  Amer¬ 
ica  the  law  of  distribution  of  terrestrial  mammals  was  for¬ 
merly  different  from  what  it  now  is.  North  America  for¬ 
merly  partook  strongly  of  the  present  character  of  the 
southern  half  of  the  continent  ;  and  the  southern  half  was 
formerly  more  closely  allied,  than  it  is  at  present,  to  the 
northern  half.  In  a  similar  manner  we  know,  from  Fal¬ 
coner  and  Cautley’s  discoveries,  that  Northern  India  was 
formerly  more  closely  related  in  its  mammals  to  Africa 
than  it  is  at  the  present  time.  Analogous,  facts  could  be 
given  in  relation  to  the  distribution  of  marine  animals. 

On  the  theory  of  descent  with  modification,  the  great  law 
of  the  long  enduring,  but  not  immutable,  succession  of  the 
same  types  within  the  same  areas,  is  at  once  explained  ;  for 
the  inhabitants  of  each  quarter  of  the  world  will  obviously 
tend  to  leave  in  that  quarter,  during  the  next  succeeding 
period  of  time,  closely  allied  though  in  some  degree  modi¬ 
fied  descendants.  If  the  inhabitants  of  one  continent  for¬ 
merly  differed  greatly  from  those  of  another  continent,  so 
will  their  modified  descendants  still  differ  in  nearly  the 
same  manner  and  degree.  But  after  very  long  intervals  of 
time,  and  after  great  geographical  changes,  permitting 
much  intermigration,  the  feebler  will  yield  to  the  more 
dominant  forms,  and  there  will  be  nothing  immutable  in 
the  distribution  of  organic  beings. 

It  may  be  asked  in  ridicule  whether  I  suppose  that  the 
megatherium  and  other  allied  huge  monsters,  which  for- 
merely  lived  in  South  America,  have  left  behind  them  the 
sloth,  armadillo,  and  ant-eater,  as  their  degenerate  descend. 


SAME  TYPES  IN  TIIE  SAME  AREAS. 


369 


ants.  This  cannot  for  an  instant  be  admitted.  These 
huge  animals  have  become  wholly  extinct,  and  have  left  no 
progeny.  But  in  the  caves  of  Brazil  there  are  many 
extinct  species  which  are  closely  allied  in  size  and  in  all 
other  characters  to  the  species  still  living  in  South  America; 
and  some  of  these  fossils  may  have  been  the  actual  progeni¬ 
tors  of  the  living  species.  It  must  not  be  forgotten  that, 
on  our  theory,  all  the  species  of  the  same  genus  are  the 
descendants  of  some  one  species ;  so  that,  if  six  genera, 
each  having  eight  species,  be  found  in  one  geological  for¬ 
mation,  and  in  a  succeeding  formation  there  be  six  other 
allied  or  representative  genera,  each  with  the  same  number 
of  species,  then  we  may  conclude  that  generally  only  one 
species  of  each  of  the  older  genera  has  left  modified 
descendants,  which  constitute  the  new  genera  containing 
the  several  species ;  the  other  seven  species  of  each  old 
genus  having  died  out  and  left  no  progeny.  Or,  and  this 
will  be  a  far  commoner  case,  two  or  three  species  in  two  or 
three  alone  of  the  six  older  genera  will  be  the  parents  of 
the  new  genera  :  the  other  species  and  the  other  old  genera 
having  become  utterly  extinct.  In  failing  orders,  with  the 
genera  and  species  decreasing  in  numbers  as  is  the  case 
with  the  Edentata  of  South  America,  still  fewer  genera 
and  species  will  leave  modified  blood-descendants. 

SUMMARY  OF  THE  PRECEDING  AND  PRESENT  CHAPTERS 

I  have  attempted  to  show  that  the  geological  record  is 
extremely  imperfect ;  that  only  a  small  portion  of  the 
globe  has  been  geologically  explored  with  care ;  that  only 
certain  classes  of  organic  beings  have  been  largely  preserved 
in  a  fossil  state;  that  the  number  both  of  specimens  and  of 
species,  preserved  in  our  museums,  is  absolutely  as  nothing 
compared  with  the  number  of  generations  which  must  have 
passed  away  even  during  a  single  formation  ;  that,  owing 
to  subsidence  being  almost  necessary  for  the  accumulation 
of  deposits  rich  in  fossil  species  of  many  kinds,  and  thick 
enough  to  outlast  future  degradation,  great  intervals  of 
time  must  have  elapsed  between  most  of  our  successive  for¬ 
mations  ;  that  there  has  probably  been  more  extinction 
during  the  periods  of  subsidence,  and  more  variation 
during  the  periods  of  elevation,  and  during  the  latter 


370 


SUMMARY  OF  TEF 


the  record  will  have  been  least  perfectly  kept ;  that  each 
single  formation  has  not  been  continuously  deposited; 
that  the  duration  of  each  formation  is  probably  short  com¬ 
pared  with  the  average  duration  of  specific  forms ;  that 
migration  has  played  an  important  part  in  the  first  appear¬ 
ance  of  new  forms  in  any  one  area  and  formation  ;  that 
widely  ranging  species  are  those  which  have  varied  most 
frequently,  and  have  oftenest  given  rise  to  new  species  ;  that 
varieties  have  at  first  been  local ;  and  lastly,  although  each 
species  must  have  passed  through  numerous  transitional 
stages,  it  is  probable  that  the  periods,  during  which  each 
underwent  modification,  though  many  and  long  as  meas¬ 
ured  by  years,  have  been  short  in  comparison  with  the 
periods  during  which  each  remained  in  an  unchanged  con¬ 
dition.  These  causes,  taken  conjointly,  will  to  a  large 
extent  explain  why — though  we  do  find  many  links — we  do 
not  find  interminable  varieties,  connecting  together  all 
extinct  and  existing  forms  by  the  finest  graduated  steps. 
It  should  also  be  constantly  borne  in  mind  that  any  linking 
variety  between  two  forms,  which  might  be  found,  would 
be  ranked,  unless  the  whole  chain  could  be  perfectly 
restored,  as  a  new  and  distinct  species ;  for  it  is  not  pre¬ 
tended  that  we  have  any  sure  criterion  hv  which  species 
and  varieties  can  be  discriminated. 

He  who  rejects  this  view  of  the  imperfection  of  the  geo¬ 
logical  record,  will  rightly  reject  the  whole  theory.  For  he 
may  ask  in  vain  where  are  the  numberless  transitional 
links  which  must  formerly  have  connected  the  closely 
allied  or  representative  species,  found  in  the  successive 
stages  of  the  same  great  formation?  He  may  disbelieve  in 
the  immense  intervals  of  time  which  must  have  elapsed 
between  our  consecutive  formations;  he  may  overlook  how 
important  a  part  migration  has  played,  when  the  forma¬ 
tions  of  any  one  great  region,  as  those  of  Europe,  are  con¬ 
sidered;  he  may  urge  the  apparent,  but  often  falsely 
apparent,  sudden  coming  in  of  whole  groups  of  species. 
He  may  ask  where  are  the  remains  of  those  infinitely  nu¬ 
merous  organisms  which  must  have  existed  long  before  the 
Cambrian  system  was  deposited?  We  now  know  that  at 
least  one  animal  did  then  exist;  but  I  can  answer  this  last 
question  only  by  supposing  that  where  our  oceans  now 
extend  they  have  extended  for  an  enormous  period,  and 


PRECEDiN G  AND  PRESENT  CHAPTERS.  37  j 

where  our  oscillating  continents  now  stand  they  have  stood 
since  the  commencement  of  the  Cambrian  system:  but. 
that,  long  before  that  epoch,  the  world  presented  a  widely 
c  lfieient  aspect;  and  that  the  older  continents,  formed  of 
01  mations  older  than  any  known  to  us,  exist  now  only  as 

remnants  in  a  metamorphosed  condition,  or  lie  still  buried 
under  the  ocean. 

Passing  from  these  difficulties,  the  other  great  leading 
tacts  m  palaeontology  agree  admirably  with  the  theory  of 
descent  with  modification  through  variation  and  natural 
selection.  \Ve  can  thus  understand  how  it  is  that  new 
species  come  in  slowly  and  successively;  how  species  of 
ctmerent  classes  do  not  necessarily  change  together,  or  at 
the  same  rate,  or  in  the  same  degree;  yet  in  the  long  run 
that  all  undergo  modification  to  some  extent.  The  ex¬ 
tinction  of  old  forms  is  the  almost  inevitable  consequence 
of  the  production  of  new  forms.  We  can  understancTwhy 
w  len  a  species  has  once  disappeared,  it  never  reappears, 
vxi oups  of  species  increase  in  numbers  slowly,  and  endure 
for  unequal  periods  of  time;  for  the  process  cf  modifica- 
lon  is  necessarily  slow,  and  depends  on  many  complex 
contingencies.  The  dominant  species  belonging  to  large 
and  dominant  groups  tend  to  leave  many  modified  descend¬ 
ants,  which  form  new  sub-groups  and  groups.  As  these 
are  formed,  the  species  of  the  less  vigorous  groups,  from 
their  inferiority  inherited  from  a  common  progenitor,  tend 
to  become  extinct  together,  and  to  leave  no  modified  off¬ 
spring  on  the  face  of  the  earth.  But  the  utter  extinction 
of  a  whole  group  of  species  has  sometimes  been  a  slow  pro¬ 
cess,  from  the  survival  of  a  few  descendants,  lingering  in 
protected  and  isolated  situations.  When  a  group  has  once 
wholly  disappeared,  it  does  not  reappear;  for  the  link  of 
generation  has  been  broken. 

We  can  understand  how  it  is  that  dominant  forms  which 
spread  widely  and  yield  the  greatest  number  of  varieties 
tend  to  people  the  world  with  allied,  but  modified,  de¬ 
scendants;  and  these  will  generally  succeed  in  displacing 
the  groups  which  are  their  inferiors  in  the  struggle  for 
existence.  Hence,  after  long  intervals  of  time,  the  pro- 
ductions  of  the  world  appear  to  have  changed  simultane- 

We  can  understand  how  it  is  that  all  the  forms  of  life. 


SUMMAR  Y  OF  CHAPTERS. 


372 

ancient  and  recent,  make  together  a  few  grand  classes. 
We  can  understand,  from  the  continued  tendency  to  di¬ 
vergence  of  character,  why  the  more  ancient  a  foi  m  is,  the 
more  it  generally  differs  from  those  now  living;  why 
ancient  and  extinct  forms  often  tend  to  fill  up  gaps  be¬ 
tween  existing  forms,  sometimes  blending  two  groups,  pre¬ 
viously  classed  as  distinct,  into  one;  but  more  commonly 
bringing  them  only  a  little  closer  together.  The  more 
ancient  a  form  is,  the  more  often  it  stands  in  some  degree 
intermediate  between  groups  now  distinct;  for  the  moie 
ancient  a  form  is,  the  more  nearly  it  will  be  related  to,  and 
consequently  resemble,  the  common  progenitor  of  groups, 
since  become  widely  divergent.  Extinct  forms  are  seldom 
directly  intermediate  between  existing  forms;  but  are  in¬ 
termediate  only  by  a  long  and  circuitous  couise  thiough 
other  extinct  and  different  forms.  We  can  clearly  see  why 
the  organic  remains  of  closely  consecutive  formations  are 
closely^ allied;  for  they  are  closely  linked  together  by  gen¬ 
eration.  We  can  clearly  see  why  the  remains  of  an  inter¬ 
mediate  formation  are  intermediate  in  character. . 

The  inhabitants  of  the  world  at  eacli  successive  period 
in  its  history  have  beaten  their  predecessors  in  the  race  for 
life,  and  are,  in  so  far,  higher  in  the  scale,  and  their 
structure  has  generally  become  more  specialized;  and  this 
may  account  for  the  common  belief  held  by  so  many  palae¬ 
ontologists,  that  organization  on  the  whole  has  progressed. 
Extinct  and  ancient  animals  resemble  to  a  certain  extent  the 
embryos  of  the  more  recent  animals  belonging  to  the  same 
classes,  and  this  wonderful  fact  receives  a  simple  explana¬ 
tion  according  to  our  views.  The  succession  of  the  same 
types  of  structure  within  the  same  areas  during  The  later 
geological  periods  ceases  to  be  mysterious,  and  is  intelligible 

on  the  principle  of  inheritance. 

If,  then,  the  geological  record  be  as  imperfect  as  many 
believe,  and  it  may  at  least  be  asserted  that  the  record  cannot 
be  proved  to  be  much  more  perfect,  the  main  objections  to 
the  theory  of  natural  selection  are  greatly  diminished  or 
disappear.  On  the  other  hand,  all  the  chief  laws  of 
paleontology  plainly  proclaim,  as  it  seems  to  me,  that 
species  have  been  produced  by  ordinary  generation:  old 
forms  having  been  supplanted  by  new  and  improved  forms 
of  life,  the  products  of  Variation  and  the  Survival  of  the 
Eittest. 


GEOGRAPHICAL  DISTRIBUTION, . 

• 


CHAPTER  XII. 

GEOGRAPHICAL  DISTRIBUTION. 

Present  distribution  cannot  be  accounted  for  by  differences  in 
physical  conditions  —  Importance  of  barriers — Affinity  of  the 
productions  of  the  same  continent — Centers  of  creation — Means 
of  dispersal  by  changes  of  climate  and  of  the  level  of  the  land, 
and  by  occasional  means — Dispersal  during  the  Glacial  period — 
Alternate  Glacial  periods  in  the  North  and  South. 

In  considering  the  distribution  of  organic  beings 
over  the  face  of  the  globe,  the  first  great  fact  which  strikes 
us  is,  that  neither  the  similarity  nor  the  dissimilarity  of 
the  inhabitants  of  various  regions  can  be  wholly  accounted 
for  by  climatal  and  other  physical  conditions.  Of  late, 
almost  every  author  who  has  studied  the  subject  has  come 
to  this  conclusion.  The  case  of  America  alone  would 
almost  suffice  to  prove  its  truth;  for  if  we  exclude  the 
arctic  and  northern  temperate  parts,  all  authors  agree  that 
one  of  the  most  fundamental  divisions  in  geographical 
distribution  is  that  between  the  New  and  the  Old  Worlds; 
yet  if  we  travel  over  the  vast  American  continent,  from 
the  central  parts  of  the  United  States  to  its  extreme  south¬ 
ern  point,  we  meet  with  the  most  diversified  conditions; 
humid  districts,  arid  deserts,  lofty  mountains,  grassy 
plains,  forests,  marshes,  lakes  and  great  rivers,  under 
almost  every  temperature.  There  is  hardly  a  climate  or 
condition  in  the  Old  World  which  cannot  be  paralleled  in 
the  New — at  least  so  closely  as  the  same  species  generally 
require.  No  doubt  small  areas  can  be  pointed  out  in  the 
Old  World  hotter  than  any  in  the  New  World;  but  these 
are  not  inhabited  by  a  fauna  different  from  that  of  the  sur¬ 
rounding  districts;  for  it  is  rare  to  find  a  group  of  organ¬ 
isms  confined  to  a  small  area,  of  which  the  conditions  are 
peculiar  in  only  a  slight  degree.  Notwithstanding  this 


374 


GEOGRAPHICAL  DISTRIBUTION. 


general  parallelism  in  the  conditions  of  Old  and  New 
Worlds,  how  widely  different  are  their  living  productions. 

Iii  the  southern  hemisphere,  if  we  compare  large  tracts 
of  land  in  Australia,  South  Africa,  and  western  oout  1 
America,  between  latitudes  25  and  35  degrees,  we  sha 
find  parts  extremely  similar  in  all  tlieir  conditions,  yet  it 
would  not  be  possible  to  point  out  three  faunas  and  floras 
more  utterly  dissimilar.  Or,  again,  we  may  compare  the 
productions  of  South  America  south  of  latitude  3o  degiees 
with  those  north  of  25  degrees,  which  consequently  are 
separated  by  a  space  of  ten  degrees  of  latitude,  and  ai  e 
exposed  to  considerably  different  conditions;  yet  they  are 
incomparably  more  closely  related  to  each  other  than  they 
are  to  the  productions  of  Australia  or  Africa  under  nearly 
the  same  climate.  Analogous  facts  could  be  given  with 

respect  to  the  inhabitants  of  the  sea.  < 

A  second  great  fact  which  strikes  us  m  our  general 
review  is,  that  barriers  of  any  kind,  or  obstacles  to  tree 
migration,  are  related  in  a  close  and  important  manner 
to  the  differences  between  the  productions  ot  various 
regions.  We  see  this  in  the  great  difference  m  nearly 
all  the  terrestrial  productions  of  the  Isew  and  Old 
Worlds,  excepting  in  the  northern  parts,  where  the  land 
almost  ioins,  and  where,  under  a  slightly  different  climate, 
there  might  have  been  free  migration  for  the  northern 
temperate  forms,  as  there  now  is  for  the  strictly  arctic  pio- 
ductions.  We  see  the  same  fact  in  the  great  difference 
between  the  inhabitants  of  Australia,  Africa  and  bouth 
America  under  the  same  latitude;  for  these  countries  aie 
almost  as  much  isolated  from  each  other  as  is  possible.  On 
each  continent,  also,  we  see  the  same  fact;  for  on  the  op¬ 
posite  sides  of  lofty  and  continuous  mountain-ranges,  ot 
great  deserts  and  even  of  large  rivers,  we  find  different 
productions;  though  as  mountain-chains,  deserts,  etc.,  aie 
not  as  impassable,  or  likely  to  have  endured  so  long,  as  the 
oceans  separating  continents,  the  differences  are  very  in¬ 
ferior  in  degree  to  those  characteristic  of  distinct  con¬ 
tinents.  . 

Turning  to  the  sea,  we  find  the  same  law.  1  he  marine 

inhabitants  of  the  eastern  and  western  shores  of  boutli 
America  are  very  distinct,  with  extremely  few  shells,  Crus¬ 
tacea,  or  echinodermata  in  common;  but  Dr.  (xuntner  nas 


GEOGRAPHICAL  DISTRIBUTION. 


375 


recently  shown  that  about  thirty  per  cent,  of  the  fishes  are 
the  same  on  the  opposite  sides  of  the  isthmus  of  Panama; 
and  this  fact  has  led  naturalists  to  believe  that  the  isthmus 
was  formerly  open.  Westward  of  the  shores  of  America, 
a  wide  space  of  open  ocean  extends,  with  not  an  island  as 
a  halting-place  for  emigrants;  here  we  have  a  barrier  of 
another  kind,  and  as  soon  as  this  is  passed  we  meet  in  the 
eastern  islands  of  the  Pacific  with  another  and  totally  dis¬ 
tinct  fauna.  So  that  three  marine  faunas  range  northward 
and  southward  in  parallel  lines  not  far  from  each  other, 
under  corresponding  climate;  but  from  being  separated 
from  each  other  by  impassable  barriers,  either  of  land  or 
open  sea,  they  are  almost  wholly  distinct.  On  the  other 
hand,  proceeding  still  further  westward  from  the  eastern 
islands  of  the  tropical  parts  of  the  Pacific,  we  encounter 
no  impassable  barriers,  and  we  have  innumerable  islands  as 
halting-places,  or  continuous  coasts,  until,  after  traveling 
over  a  hemisphere,  we  come  to  the  shores  of  Africa;  and 
over  this  vast  space  we  meet  with  no  well-defined  and  dis¬ 
tinct  marine  faunas.  Although  so  few  marine  animals  are 
common  to  the  above-named  three  approximate  faunas  of 
Eastern  and  Western  America  and  the  eastern  Pacific 
islands,  yet  many  fishes  range  from  the  Pacific  into  the 
Indian  Ocean,  and  many  shells  are  common  to  the  eastern 
islands  of  the  Pacific  and  the  eastern  shores  of  Africa  on 
almost  exactly  opposite  meridians  of  longitude. 

A  third  great  fact,  partly  included  in  the  foregoing 
statement,  is  the  affinity  of  the  productions  of  the  same 
continent  or  of  the  same  sea,  though  the  species  themselves 
are  distinct  at  different  points  and’stations.  It  is  a  law  of 
the  widest  generality,  and  every  continent  offers  innum¬ 
erable  instances.  Nevertheless,  the  naturalist,  in  travel¬ 
ing,  for  instance,  from  north  to  south,  never  fails  to  be 
struck  by  the  manner  in  which  successive  groups  of  beings, 
specifically  distinct,  though  nearly  related,  replace  each 
other.  He  hears  from  closely  allied,  yet  distinct  kinds  of 
birds,  notes  nearly  similar,  and  sees  their  nests  similarly  con¬ 
structed,  but  not  quite  alike,  with  eggs  colored  in  nearly  the 
same  manner.  The  plains  near  the  Straits  of  Magellan  are 
inhabited  by  one  species  of  Rhea  (American  ostrich),  and 
northward  the  plains  of  La  Plata  by  another  species  of  the 
same  genus;  and  not  by  a  true  ostrich  or  emu,  like  those 


376  GEOGRAPHICAL  DISTRIBUTION. 

inhabiting  Africa  and  Australia  under  the  same  latitude. 
On  these  same  plains  of  La  Plata  we  see  the  agouti 
and  bizcacha,  animals  having  nearly  the  same  habits  as 
our  hares  and  rabbits,  and  belonging  to  the  same  order  of 
rodents,  but  they  plainly  display  an  American  type  of 
structure.  We  ascend  the  lofty  peaks  of  the  Cordillera, 
and  we  find  an  alpine  species  of  bizcacha;  we  look  to  the 
waters,  and  we  do  not  find  the  beaver  or  muskrat,  but  the 
'  coypu  and  capybara,  rodents  of  the  South  American  type. 
Innumerable  other  instances  could  be  given.  If  we  look  to 
the  islands  off  the  American  shore,  however  much  they  may 
differ  in  geological  structure,  the  inhabitants  _  are  essen¬ 
tially  American,  though  they  may  be  all  peculiar  species. 
We  may  look  back  to  past  ages,  as  shown  in  the  last 
chapter,  and  we  find  American  types  then  prevailing  on  the 
American  continent  and  in  the  American  seas.  We  see  in 
these  facts  some  deep  organic  bond,  throughout  space  and 
time,  over  the  same  areas  of  land  and  water,  independently 
of  physical  conditions.  The  naturalist  must  be  dull  who 
is  not  led  to  inquire  what  this  bond  is. 

The  bond  is  simply  inheritance,  that  cause  which  alone, 
as  far  as  we  positively  know,  produces  organisms  quite  like 
each  other,  or,  as  we  see  in  the  case  of  varieties,  nearly 
alike.  The  dissimilarity  of  the  inhabitants  of  different 
regions  may  be  attributed  to  modification  through  variation 
and  natural  selection,  and  probably  in  a  subordinate  degree 
to  the  definite  influence  of  different  physical  conditions. 
The  degrees  of  dissimilarity  will  depend  on  the  migration 
of  the  more  dominant  forms  of  life  from  one  region  into 
another  having  been  more  or  less  effectually  prevented,  at 
periods  more  or  less  remote — on  the  nature  and  number  of 
the  former  immigrants — and  on  the  action  of  the  inhab¬ 
itants  on  each  other  in  leading  to  the  preservation  of  differ¬ 
ent  modifications;  the  relation  of  organism  to  organism  in 
the  struggle  for  life  being,  as  I  Jiave  already  often  re¬ 
marked,  the  most  important  of  all  relations.  Thus  the 
high  importance  of  barriers  comes  into  play  by  checking 
migration;  as  does  time  for  the  slow  process  of  modifica¬ 
tion  through  natural  selection.  Widely-ranging  species, 
abounding  in  individuals,  which  have  already  triumphed 
over  many  competitors  in  their  own  widely-extended  homes, 
will  have  the  best  chance  of  seizing  on  new  places,  when 


GEOGRAPHICAL  DISTRIBUTION. 


377 


they  spread  out  into  new  countries.  In  their  new  homes 
they  will  be  exposed  to  new  conditions,  and  will  frequently 
undergo  further  modification  and  improvement;  and  thus 
they  will  become  still  further  victorious,  and  will  produce 
groups  of  modified  descendants.  On  this  principle  of  in¬ 
heritance  with  modification  we  can  understand  how  it  is 
that  sections  of  genera,  whole  genera,  and  even  families, 
are  confined  to  the  same  areas,  as  is  so  commonly  and  noto¬ 
riously  the  case. 

There  is  no  evidence,  as  was  remarked  in  the  last 
chapter,  of  the  existence  of  any  law  of  necessary  develop¬ 
ment.  As  the  variability  of  each  species  is  an  independent 
property,  and  will  be  taken  advantage  of  by  natural  selec¬ 
tion,  only  so  far  as  it  profits  each  individual  in  its  complex 
struggle  for  life,  so  the  amount  of  modification  in  different 
species  will  be  no  uniform  quantity.  If  a  number  of  species, 
after  having  long  competed  with  each  other  in  their  old 
home,  were  to  migrate  in  a  body  into  a  new  and  afterward 
isolated  country,  they  would  be  little  liable  to  modification ; 
for  neither  migration  nor  isolation  in  themselves  effect  any 
thing.  These  principles  come  into  play  only  by  bringing 
organisms  into  new  relations  with  each  other  and  in  a  lesser 
degree  with  the  surrounding  physical  conditions.  As  wc 
have  seen  in  the  last  chapter  that  some  forms  have  retained 
nearly  the  same  character  from  an  enormously  remote 
geological  period,  so  certain  species  have  migrated  over 
vast  spaces,  and  have  not  become  greatly  or  at  all  modified. 

According  to  these  views,  it  is  obvious  that  the  several 
species  of  the  same  genus,  though  inhabiting  the  most 
distant  quarters  of  the  world,  must  originally  have  pro¬ 
ceeded  from  the  same  source,  as  they  are  descended 
from  the  same  progenitor.  In  the  case  of  those 
species  which  have  undergone,  during  whole  geological 
periods,  little  modification,  there  is  not  much  difficulty  in 
believing  that  they  have  migrated  from  the  same  region; 
for  during  the  vast  geographical  and  climatical  changes 
which  have  supervened  since  ancient  times,  almost  any 
amount  of  migration  is  possible.  But  in  many  other  cases, 
in  which  we  have  reason  to  believe  that  the  species  of  a 
genus  have  been  produced  within  comparatively  recent 
times,  there  is  great  difficulty  on  this  head.  It  is  also 
obvious  that  the  individuals  of  the  same  species,,  though 


378 


SINGLE  CENTERS  OF  CREATION 


now  inhabiting  distant  and  isolated  regions,  must  have 
proceeded  from  one  spot,  where  their  parents  were  first 
produced:  for,  as  has  been  explained,  it  is  incredible  that 
individuals  indentically  the  same  should  have  been  pro¬ 
duced  from  parents  specifically  distinct. 

SINGLE  CENTERS  OF  SUPPOSED  CREATION. 

We  are  thus  brought  to  the  question  which  has  been 
largely  discussed  by  naturalists,  namely,  whether  species 
have  been  created  at  one  or  more  points  of  the  earth's  sur¬ 
face.  Undoubtedly  there  are  many  cases  of  extreme  diffi¬ 
culty  in  understanding  how  the  same  species  could  possi¬ 
bly  have  migrated  from  some  one  point  to  the  several  dis¬ 
tant  and  isolated  points,  where  now  found.  Nevertheless 
the  simplicity  of  the  view  that  each  species  was  first  pro¬ 
duced  within  a  single  region  captivates  the  mind.  He  who 
rejects  it,  rejects  the  vera  causa  of  ordinary  generation 
with  subsequent  migration,  and  calls  in  the  agency  of  a 
miracle.  It  is  universally  admitted,  that  in  most  cases  the 
area  inhabited  by  a  species  is  continuous;  and  that  when  a 
plant  or  animal  inhabits  two  points  so  distant  from  each 
other,  or  with  an  interval  of  such  a  nature,  that  the  space 
could  not  have  been  easily  passed  over  by  migration,  the 
fact  is  given  as  something  remarkable  and  exceptional. 
The  incapacity  of  migrating  across  a  wide  sea  is  more  clear 
in  the  case  of  terrestrial  mammals  than  perhaps  with  any 
other  organic  beings;  and,  accordingly,  we  find  no  inex¬ 
plicable  instances  of  the  same  mammals  inhabiting  distant 
points  of  the  world.  No  geologist  feels  any  difficulty  in 
Great  Britain  possessing  the  same  quadrupeds  with  the 
rest  of  Europe,  for  they  were  no  doubt  once  united.  But 
if  the  same  species  can  be  produced  at  two  separate  points, 
why  do  we  not  find  a  single  mammal  common  to  Europe 
and  Australia  or  South  America?  The  conditions  of  life 
are  nearly  the  same,  so  that  a  multitude  of  European 
animals  and  plants  have  become  naturalized  in  America 
and  Australia;  and  some  of  the  aboriginal  plants  are 
identically  the  same  at  these  distant  points  of  the 
northern  and  southern  hemispheres?  The  answer,  as 
I  believe,  is,  that  mammals  have  not  been  able  to 
migrate,  whereas  gome  plants,  from  their  varied  means 


SINGLE  CENTERS  OF  CREATION. 


m 

of  dispersal,  have  migrated  across  the  wide  and  broken 
interspaces.  The  great  and  striking  influence  of  barriers 
of  all  kinds,  is  intelligible  only  on  the  view  that  the  great 
majority  of  species  have  been  produced  on  one  side,  and 
have  not  been  able  to  migrate  to  the  opposite  side.  Some 
few  families,  many  subfamilies,  very  many  genera,  a  still 
greater  number  of .  sections  of  genera,  are  confined  to  a 
single  region;  and  it  has  been  observed  by  several  natural¬ 
ists  that  the  most  natural  genera,  or  those  genera  in  which 
the  species  are  most  closely  related  to  each  other,  are  gen¬ 
erally  confined  to  the  same  country,  or  if  they  have  a  wide 
range  that  their  range  is  continuous.  What  a  strange 
anomaly  it  would  be  if  a  directly  opposite  rule  were  to 
prevail  when  we  go  down  one  step  lower  in  the  series, 
namely,  to  the  individuals  of  the  same  species,  and 
these  had  not  been,  at  least  at  first,  confined  to  some  one 
region! 

Hence,  it  seems  to  me,  as  it  has  to  many  other  natu¬ 
ralists,  that  the  view  of  each  species  having  been  produced 
in  one  area  alone,  and  having  subsequently  migrated  from 
that  area  as  far  as  its  powers  of  migration  and  subsistence 
under  past  and  present  conditions  permitted,  is  the  most 
probable.  Undoubtedly  many  cases  occur  in  which  we 
cannot  explain  how  the  same  species  could  have  passed  from 
one  point  to  the  other.  But  the  geographical  and  climatical 
changes  which  have  certainly  occurred  within  recent  geo¬ 
logical  times,  must  have  rendered  discontinuous  the  for¬ 
merly  continuous  range  of  many  species.  So  that  we  are 
reduced  to  consider  whether  the  exceptions  to  continuity  of 
range  are  so  numerous,  and  of  so  grave  a  nature,  that  we 
ought  to  give  up  the  belief,  rendered  probable  by  general 
considerations,  that  each  species  has  been  produced  within 
one  area,  and  has  migrated  thence  as  far  as  it  could.  It 
would  be  hopelessly  tedious  to  discuss  all  the  exceptional 
cases  of  the  same  species,  now  living  at  distant  and  sep¬ 
arated  points,  nor  do  I  for  a  moment  pretend  that  any 
explanation  could  be  offered  of  many  instances.  But, 
after  some  preliminary  remarks,  I  will  discuss  a  few  of  the 
most  striking  classes  of  facts,  namely,  the  existence  of  the 
same  species  on  the  summits  of  distant  mountain  ranges, 
and  at  distant  points  in  the  Arctic  and  Antarctic  regions; 
and  secondly  (in  the  following  chapter),  the  wide  distri- 


SINGLE  CENTERS  OF  CREATION. 


380 

bution  of  fresh  water  productions;  and  thirdly,  the 
occurrence  of  the  same  terrestrial  species  on  islands  and 
on  the  nearest  mainland,  though  separated  by  hundreds  of 
miles  of  open  sea.  If  the  existence  of  the  same  species  at 
distant  and  isolated  points  of  the  earth,s  surface  can  in 
many  instances  be  explained  on  the  view  of  each  species 
having  migrated  from  a  single  birthplace,  then,  consider¬ 
ing  our  ignorance  with  respect  to  former  climatical  and  geo¬ 
graphical  changes,  and  to  the  various  occasional  means  of 
transport,  the  belief  that  a  single  birthplace  is  the  law 
seems  to  me  incomparably  the  safest. 

In  discussing  this  subject  we  shall  be  enabled  at  the 
same  time  to  consider  a  point  equally  important  for  us, 
namely,  whether  the  several  species  of  a  genus  which  must 
on  our  theory  all  be  descended  from  a  common  progenitor, 
can  have  migrated,  undergoing  modification  during  their 
migration  from  some  one  area.  If,  when  most  of  the  spe¬ 
cies  inhabiting  one  region  arc  different  from  those  of  another 
region,  though  closely  allied  to  them,  it  can  be  shown  that 
migration  from  the  "one  region  to  the  other  has  probably 
occurred  at  some  former  period,  our  general  view  will  be  much 
strengthened;  for  the  explanation  is  obvious  on  the  principle 
of  descent  with  modification.  A  volcanic  island,  for  in¬ 
stance,  upheaved  and  formed  at  the  distance  of  a  few 
hundreds  of  miles  from  a  continent,  would  probably  receive 
from  it  in  the  course  of  time  a  few  colonists,  and  their 
descendants,  though  modified,  would  still  be  related  by 
inheritance  to  the  inhabitants  of  that  continent.  Cases  of 
this  nature  are  common,  and  are,  as  we  shall  hereafter  see, 
inexplicable  on  the  theory  of  independent  creation.  This 
view  of  the  relation  of  the  species  of  one  region  to  those  of 
another,  does  not  differ  much  from  that  advanced  by  Mr. 
Wallace,  who  concludes  that  “  every  species  has  come  into 
existence  coincident  both  in  space  and  time  with  a  pre¬ 
existing  closely  allied  species.”  And  it  is  now  well  known 
that  he  attributes  this  coincidence  to  descent  with  modi¬ 
fication. 

The  question  of  single  or  multiple  centres  of  creation 
differs  from  another  though  allied  question,  namely, 
whether  all  individuals  of  the  same  species  are  descended 
from  a  single  pair,  or  single  hermaphrodite,  or  whether,  as 
some  authors  suupose,  from  many  individuals  simultane- 


MEANS  OF  DISPERSAL. 


381 


ously  created.  With  organic  beings  which  never  intercross, 
if  such  exist,  each  species  must  be  descended  from  a  suc¬ 
cession  of  modified  varieties,  that  have  supplanted  each 
other,  but  have  never  blended  with  other  individuals  or 
varieties  of  the  same  species;  so  that,  at  each  successive 
stage  of  modification,  all  the  individuals  of  the  same  form 
will  be  descended  from  a  single  parent.  But  in  the  great 
majority  of  cases,  namely,  with  all  organisms  which  habit¬ 
ually  unite  for  each  birth,  or  which  occasionally  intercross, 
the  individuals  of  the  same  species  inhabiting  the  same 
area  will  be  kept  nearly  uniform  by  intercrossing;  so  that 
many  individuals  will  go  on  simultaneously  changing,  and 
the  whole  amount  of  modification  at  each  stage  will  not  be 
due  to  descent  from  a  single  parent.  To  illustrate  what  I 
mean:  our  English  race-horses  differ  from  the  horses  of 
every  other  breed;  but  they  do  not  owe  their  difference  and 
superiority  to  descent  from  any  single  pair,  but  to  continued 
care  in  the  selecting  and  training  of  many  individuals 
during  each  generation. 

Before  discussing  the  three  classes  of  facts,  which  I  have 
selected  as  presenting  the  greatest  amount  of  difficulty  on 
the  theory  of  “  single  centers  of  creation,”  I  must  say  a 
few  words  on  the  means  of  dispersal. 

MEANS  OF  DISPERSAL. 

Sir  C.  Lyell  and  other  authors  have  ably  treated  this 
subject.  I  can  give  here  only  the  briefest  abstract  of  the 
more  important  facts.  Change  of  climate  must  have  had 
a  powerful  influence  on  migration.  A  region  now  impass¬ 
able  to  certain  organisms  from  the  nature  of  its  climate, 
might  have  been  a  high  road  for  migration,  when  the 
climate  was  different.  I  shall,  however,  presently  have  to 
discuss  this  branch  of  the  subject  in  some  detail.  "Changes 
of  level  in  the  land  must  also  have  been  highly  influential: 
a  narrow  isthmus  now  separates  two  marine  faunas;  sub¬ 
merge  it,  or  let  it  formerly  have  been  submerged, 
and  the  two  faunas  will  now  blend  together,  or  may 
formerly  have  blended.  Where  the  sea  now  extends, 
land  may  at  a  former  period  have  connected  islands  or  pos¬ 
sibly  even  continents  together,  and  thus  have  allowed  terres¬ 
trial  productions  to  pass  from  one  to  the  other.  No  geologist 


382 


MEANS  OF  DISPERSAL. 


disputes  that  great  mutations  of  level  have  occurred  within 
the  period  of  existing  organisms.  Edward  Forbes  insisted 
that  all  the  islands  in  the  Atlantic  must  have  been  recently 
connected  with  Europe  or  Africa,  and  Europe  likewise 
with  America.  Other  authors  have  thus  hypothetically 
bridged  over  every  ocean,  and  united  almost  every  island 
with  some  mainland.  If,  indeed,  the  arguments  used  by 
Eorbes  are  to  be  trusted,  it  must  be  admitted  that 
scarcely  a  single  island  exists  which  has  not  recently 
been  united  to  some  continent.  This  view  cuts  the 
Gordian  knot  of  the  dispersal  of  the  same  species  to  the 
most  distant  points,  and  removes  many  a  difficulty;  but  to 
the  best  of  my  judgment  we  are  not  authorized  in  admit¬ 
ting  such  enormous  geographical  changes  within  the  period 
of  existing  species.  It  seems  to  me  that  we  have  abundant 
evidence  of  great  oscillations  in  the  level  of  the  land  or 
sea;  but  not  of  such  vast  changes  in  the  position  and  ex¬ 
tension  of  our  continents,  as  to  have  united  them  within 
the  recent  period  to  each  other  and  to  the  several  interven¬ 
ing  oceanic  islands.  I  freely  admit  the  former  existence 
of  many  islands,  now  buried  beneath  the  sea,  which  may 
have  served  as  halting-places  for  plants  and  for  many 
animals  during  their  migration.  In  the  coral-producing 
oceans  such  sunken  islands  are  now  marked  by  rings  of 
coral  or  atolls  standing  over  them.  Whenever  it  is  fully 
admitted,  as  it  will  some  day  be,  that  each  species  has 
proceeded  from  a  single  birthplace,  and  when  in  the  course 
of  time  we  know  something  definite  about  the  means  of 
distribution,  we  shall  be  enabled  to  speculate  with  security 
on  the  former  extension  of  the  land.  But  I  do  not  believe 
that  it  will  ever  be  proved  that  within  the  recent  period 
most  of  our  continents  which  now  stand  quite  separate, 
have  been  continuously,  or  almost  continuously  united 
with  each  other,  and  with  the  many  existing  oceanic 
islands.  Several  facts  in  distribution — such  as  the  great 
difference  in  the  marine  faunas  on  the  opposite  sides  of 
almost  every  continent — the  close  relation  of  the  tertiary 
inhabitants  of  several  lands  and  even  seas  to  their  present 
inhabitants — the  degree  of  affinity  between  the  mammals 
inhabiting  islands  with  those  of  the  nearest  continent, 
being  in  part  determined  (as  we  shall  hereafter  see)  by  the 
depth  of  the  intervening  ocean — these  and  other  such 


MEANS  OF  DISPERSAL. 


383 


facts  are  opposed  to  the  admission  of  such  prodigious  geo¬ 
graphical  revolutions  within  the  recent  period,  as  are 
necessary  on  the  view  advanced  by  Forbes  and  admitted  by 
his  followers.  The  nature  and  relative  proportions  of  the 
inhabitants  of  oceanic  islands  are  likewise  opposed  to  the 
belief  of  their  former  continuity  of  continents.  Nor  does 
the  almost  universally  volcanic  composition  of  such  islands 
favor  the  admission  that  they  are  the  wrecks  of  sunken 
continents;  if  they  had  originally  existed  as  continental 
mountain  ranges,  some  at  least  of  the  islands  would  have 
been  formed,  like  other  mountain  summits,  of  granite, 
metamorphic  schists,  old  fossiliferous  and  other  rocks,  in¬ 
stead  of  consisting  of  mere  piles  of  volcanic  matter. 

I  must  now  say  a  few  words  on  what  are  called  acci¬ 
dental  means,  but  which  more  properly  should  he  called 
occasional  means  of  distribution.  I  shall  here  confine 
myself  to  plants.  In  botanical  works,  this  or  that  plant 
is  often  stated  to  be  ill  adapted  for  wide  dissemination; 
but  the  greater  or  less  facilities  for  transport  across  the 
sea  may  be  said  to  be  almost  wholly  unknown.  Until 
I  tried,  with  Mr.  Berkeley^  aid,  a  few  experiments,  it 
was  not  even  known  how  far  seeds  could  resist  the  in¬ 
jurious  action  of  sea-water.  To  my  surprise  I  found 
that  out  of  eighty-seven  kinds,  sixty-four  germinated 
after  an  immersion  of  twenty-eight  days,  and  a  few 
survived  an  immersion  of  137  days.  It  deserves  notice 
that  certain  orders  were  far  more  injured  than  others:  nine 
Leguminosse  were  tried,  and,  with  one  exception,  they 
resisted  the  salt-water  badly;  seven  species  of  the  allied 
orders,  Hydrophyllaceas  and  Polemoniaceaj,  were  all  killed 
by  a  month's  immersion.  For  convenience  sake  I  chiefly 
tried  small  seeds  without  the  capsules  or  fruit;  and  as  all 
of  these  sunk  in  a  few  days,  they  could  not  have  been 
floated  across  wide  spaces  of  the  sea,  whether  or  not  they 
were  injured  by  salt  water.  Afterward  I  tried  some  larger 
fruits,  capsules,  etc.,  and  some  of  these  floated  for  a  long 
time.  It  is  well  known  what  a  difference  there  is  in  the 
buoyancy  of  green  and  seasoned  timber;  and  it  occurred 
to  me  that  floods  would  often  wash  into  the  sea  dried 
plants  or  branches  with  seed-capsules  or  fruit  attached  to 
them.  Hence  I  was  led  to  dry  the  stems  and  branches  of 
ninety-four  plants  with  ripe  fruit,  and  to  place  them  on 


384 


MEANS  OF  DISPERSAL. 


sea-water.  The  majority  sunk  quickly,  but  some  which, 
while  green,  floated,  for  a  very  short  time,  when  dried, 
floated  much  longer;  for  instance,  ripe  hazel-nuts  sunk 
immediately,  but  when  dried  they  floated  for  ninety  days, 
and  afterward  when  planted  germinated;  an  asparagus- 
plant  with  ripe  berries  floated  for  twenty-three  days,  wdien 
dried  it  floated  for  eighty-five  days,  and  the  seeds  after¬ 
ward  germinated;  the  ripe  seeds  of  Helosciadium  sunk  in 
two  days,  when  dried  they  floated  for  above  ninety  days, 
and  afterward  germinated.  Altogether,  out  of  the  ninety- 
four  dried  plants,  eighteen  floated  for  above  twenty-eight 
days;  and  some  of  the  eighteen  floated  for  a  very  much  longer 
period.  So  that  as -§4  kinds  of  seeds  germinated  after  an 
immersion  of  twenty-eight  days;  and  as  distinct  species 
with  ripe  fruit  (but  not  all  the  same  species  as  in  the  forego¬ 
ing  experiment)  floated,  after  being  dried,  for  above  twenty- 
eight  days,  we  may  conclude,  as  far  as  anything  can  be 
inferred  from  these  scanty  facts,  that  the  seeds  of  y1^ 
kinds  of  plants  of  any  country  might  be  floated  by  sea- 
currents  during  twenty-eight  days,  and  would  retain  their 
power  of  germination.  In  Johnston's  Physical  Atlas,  the 
average  rate  of  the  several  Atlantic  currents  is  thirty-three 
miles  per  diem  (some  currents  running  at  the  rate  of  sixty 
miles  per  diem);  on  this  average,  the  seeds  of  plants 
belonging  to  one  country  might  be  floated  across  924  miles 
of  sea  to  another  country,  and  when  stranded,  if  blown  by 
an  inland  gale  to  a  favorable  spot,  would  germinate. 

Subsequently  to  my  experiments,  M.  Martens  tried  sim¬ 
ilar  ones,  but  in  a  much  better  manner,  for  he  placed  the 
seeds  in  a  box  in  the  actual  sea,  so  that  they  were  alter¬ 
nately  wet  and  exposed  to  the  air  like  really  floating 
plants.  He  tried  ninety-eight  seeds,  mostly  different  from 
mine,  but  he  chose  many  large  fruits,  and  likewise  seeds, 
from  plants  which  live  near  the  sea;  and  this  would  have 
favored  both  the  average  length  of  their  flotation  and  their 
resistance  to  the  injurious  action  of  the  salt-water.  On 
the  other  hand,  he  did  not  previously  dry  the  plants  or 
branches  with  the  fruit;  and  this,  as  we  have  seen,  would 
have  caused  some  of  them  to  have  floated  much  longer. 
The  result  was  that  -£-f  of  his  seeds  of  different  kinds 
floated  for  forty-two  days,  and  were  then  capable  of  ger¬ 
mination.  But  I  do  not  doubt  that  plants  exposed  to  the 


MEANS  OF  DISPERSAL. 


385 


waves  would  float  for  a  less  time  than  those  protected  from 
violent  movement  as  in  our  experiments.  Therefore,  it 
would  perhaps  be  safer  to  assume  that  the  seeds  of  about 
■jW  plants  of  a  flora,  after  having  been  dried,  could  be 
floated  across  a  space  of  sea  900  miles  in  width,  and  would 
then  germinate.  The  facts  of  the  larger  fruits  often  float¬ 
ing  longer  than  the  small,  is  interesting;  as  plants  with 
large  seeds  or  fruit  which,  as  Alph.  de  Candolle  has  shown, 
generally  have  restricted  ranges,  could  hardly  be  trans¬ 
ported  by  any  other  means. 

Seeds  may  be  occasionally  transported  in  another 
manner.  Drift  timber  is  thrown  up  on  most  islands, 
even  on  those  in  the  midst  of  the  widest  oceans;  and  the 
natives  of  the  coral  islands  in  the  Pacific  procure  stones 
for  their  tools,  solely  from  the  roots  of  drifted  trees,  these 
stones  being  a  valuable  royal  tax.  I  find  that  when  irregu¬ 
larly  shaped  stones  are  embedded  in  the  roots  of  trees, 
small  parcels  of  earth  are  frequently  inclosed  in  their  inter¬ 
stices  and  behind  them,  so  perfectly  that  not  a  particle 
could  be  washed  away  during  the  longest  transport:  out  of 
one  small  portion  of  earth  thus  completely  inclosed  by  the 
roots  of  an  oak  about  fifty  years  old,  three  dicotyledonous 
plants  germinated:  I  am  certain  of  the  accuracy  of  this 
observation.  Again,  I  can  show  that  the  carcasses  of  birds, 
when  floating  on  the  sea,  sometimes  escape  being  immedi¬ 
ately  devoured:  and  many  kinds  of  seeds  in  the  crops  of 
floating  birds  long  retain  their  vitality:  peas  and  vetches, 
for  instance,  are  killed  by  even  a  few  days*  immersion  in 
sea-water;  but  some  taken  out  of  the  crop  of  a  pigeon, 
which  had  floated  on  artificial  sea-water  for  thirty  days,  to 
my  surprise  nearly  all  germinated. 

Living  birds  can  hardly  fail  to  be  highly  effective  agents 
in  the  transportation  of  seeds.  I  could  give  many  facts 
showing  how  frequently  birds  of  many  kinds  are  blown  by 
gales  to  vast  distances  across  the  ocean.  We  may  safely 
assume  that  under  such  circumstances  their  rate  of  flight 
would  often  be  thirty-five  miles  an  hour;  and  some  authors 
have  given  a  far  higher  estimate.  I  have  never  seen  an 
instance  of  nutritious  seeds  passing  through  the  intestines 
of  a  bird;  but  hard  seeds  of  fruit  pass  uninjured  through 
even  the  digestive  organs  of  a  turkey.  In  the  course  of 
two  months,  I  picked  up  in  my  garden  twelve  kinds  of 


386 


MEANS  OE  DISPERSAL. 


seeds,  out  of  the  excrement  of  small  birds,  and  these 
seemed  perfect,  and  some  of  them,  which  were  tried,  ger¬ 
minated.  But  the  following  fact  is  more  important:  the 
crops  of  birds  do  not  secrete  gastric  juice,  and  do  not,  as  I 
know  by  trial,  injure  in  the  least  the  germination  of  seeds; 
now,  after  a  bird  has  found  and  devoured  a  large  supply  of 
food,  it  is  positively  asserted  that  all  the  grains  do  not  pass 
into  the  gizzard  for  twelve  or  even  eighteen  hours.  A 
bird  in  this  interval  might  easily  be  blown  to  the  distance 
of  five  hundred  miles,  and  hawks  are  known  to  look  out 
for  tired  birds,  and  the  contents  of  their  torn  crops  might 
thus  readily  get  scattered.  Some  hawks  and  owls  bolt 
their  prey  whole,  and,  after  an  interval  of  from  twelve  to 
twenty  hours,  disgorge  pellets,  which,  as  I  know  from  ex¬ 
periments  made  in  the  Zoological  Gardens,  include  seeds 
capable  of  germination.  Some  seeds  of  the  oat,  wheat, 
millet,  canary,  hemp,  clover,  and  beet  germinated  after 
having  been  from  twelve  to  twenty-one  hours  in  the 
stomachs  of  different  birds  of  prey;  and  two  seeds  of  beet 
grew  after  having  been  thus  retained  for  two  days  and 
fourteen  hours.  Fresh-water  fish,  I  find,  eat  seeds  of  many 
land  and  water  plants;  fish  are  frequently  devoured  by 
birds,  and  thus  the  seeds  might  be  transported  from  place 
to  place.  I  forced  many  kinds  of  seeds  into  the  stomachs 
of  dead  fish,  and  then  gave  their  bodies  to  fishing-eagles, 
storks,  and  pelicans;  these  birds,  after  an  interval  of  many 
hours,  either  rejected  the  seeds  in  pellets  or  passed. them  in 
their  excrement;  and  several  of  these  seeds  retained  the 
power  of  germination.  Certain  seeds,  however,  were 
always  killed  by  this  process. 

Locusts  are  sometimes  blown  to  great  distances  from  the 
land.  I  myself  caught  one  370  miles  from  the  . coast  of 
Africa,  and  have  heard  of  others  caught  at  greater  distances. 
The  Rev.  R.  T.  Lowe  informed  Sir  C.  Lyell  that  in  No¬ 
vember,  1844,  swarms  of  locusts  visited  the  island  of 
Madeira.  They  were  in  countless  numbers,  as  thick  as 
the  flakes  of  snow  in  the  heaviest  snowstorm,  and  extended 
upward  as  far  as  could  be  seen  with  a  telescope.  During 
two  or  three  days  they  slowly  careered  round  and  round  in 
an  immense  ellipse,  at  least  five  or  six  miles  in  diameter, 
and  at  night  alighted  on  the  taller  trees,  which  were  com¬ 
pletely  coated  with  them.  They  then  disappeared  over  the 


MEANS  OF  DISPERSAL. 


387 


sea,  as  suddenly  as  they  had  appeared,  and  have  not  since 
visited  the  island.  Now,  in  parts  of  Natal  it  is  believed  by 
some  farmers,  though  on  insufficient  evidence,  that  injuri¬ 
ous  seeds  are  introduced  into  their  grass-land  in  the  dung 
left  by  the  great  flights  of  locusts  which  often  visit  that 
country.  In  consequence  of  this  belief  Mr.  Weale  sent  me 
in  a  letter  a  small  packet  of  the  dried  pellets,  out  of  which 
I  extracted  under  the  microscope  several  seeds,  and  raised 
from  them  seven  grass  plants,  belonging  to  two  species,  of 
two  genera.  Hence  a  swarm  of  locusts,  such  as  that 
which  visited  Madeira,  might  readily  be  the  means  of  in¬ 
troducing  several  kinds  of  plants  into  an  island  lying  far 
from  the  mainland. 

Although  the  beaks  and  feet  of  birds  are  generally  clean, 
earth  sometimes  adheres  to  them:  in  one  case  I  removed 
sixty-one  grains,  and  in  another  case  twenty-two  grains  of 
dry  argillaceous  earth  from  the  foot  of  a  partridge,  and  in 
the  earth  there  was  a  pebble  as  large  as  the  seed  of  a  vetch. 
Here  is  a  better  case:  the  leg  of  a  woodcock  was  sent  to 
me  by  a  friend,  with  a  little  cake  of  dry  earth  attached  to 
the  shank,  weighing  only  nine  grains;  and  this  contained 
a  seed  of  the  toad-rush  (Juncus  bufonius)  which  germin¬ 
ated  and  flowered.  Mr.  Swaysland,  of  Brighton,  who  dur¬ 
ing  the  last  forty  years  has  paid  close  attention  to  our 
migratory  birds,  informs  me  that  he  has  often  shot  wag¬ 
tails  (Motacillse),  wheatears,  and  whinchats  (Saxicolae),  on 
their  first  arrival  on  our  shores,  before  they  had  alighted ; 
and  he  has  several  times  noticed  little  cakes  of  earth 
attached  to  their  feet.  Many  facts  could  be  given  showing 
how  generally  soil  is  charged  with  seeds.  For  instance. 
Professor  Newton  sent  me  the  leg  of  a  red-legged  partridge 
(Caccabis  rufa)  which  had  been  wounded  and  could  not 
fly,  with  a  ball  of  hard  earth  adhering  to  it,  and  weighing 
six  and  a  half  ounces.  The  earth  had  been  kept  for  three 
years,  but  when  broken,  watered  and  placed  under  a  bell 
glass,  no  less  than  eighty-two  plants  sprung  from  it:  these 
consisted  of  twelve  monocotyledons,  including  the  common 
oat,  and  at  least  one  kind  of  grass,  and  of  seventy  dicotyle¬ 
dons,  which  consisted,  judging  from  the  young  leaves,  of 
at  least  three  distinct  species.  With  such  facts  before  us, 
can  we  doubt  that  the  many  birds  which  are  annually 
blown  by  gales  across  great  spaces  of  ocean,  and  which  an- 


388 


MEAN'S  OF  DISPERSAL. 


nually  migrate — for  instance,  tlie  millions  of  quails  across 
the  Mediterranean — must  occasionally  transport  a  few 
seeds  imbedded  in  dirt  adhering  to  their  feet  or  beaks? 
But  I  shall  have  to  recur  to  this  subject. 

As  icebergs  are  known  to  be  sometimes  loaded  with  earth 
and  stones,  and  have  even  carried  brushwood,  bones, 
and  the  nest  of  a  land-bird,  it  can  hardly  be  doubted  that 
they  must  occasionally,  as  suggested  by  Lyell,  have  trans¬ 
ported  seeds  from  one  part  to  another  of  the  arctic  and 
antarctic  regions  ;  and  during  the  Glacial  period  from  one 
part  of  the  now  temperate  regions  to  another.  In  the 
Azores,  from  the  large  number  of  plants  common  to 
Europe,  in  comparison  with  the  species  on  the  other 
islands  of  the  Atlantic,  which  stand  nearer  to  the  main¬ 
land,  and  (as  remarked  by  Mr.  H.  C.  Watson)  from  their 
somewhat  northern  character,  in  comparison  with  the  lati¬ 
tude,  I  suspected  that  these  islands  had  been  partly  stocked 
by  ice-born  seeds  during  the  Glacial  epoch.  At  my  request 
Sir  0.  Lyell  wrote  to  M.  Hartung  to  inquire  whether  he 
had  observed  erratic  bowlders  on  these  islands,  and  he 
answered  that  he  had  found  large  fragments  of  granite  and 
other  rocks,  which  do  not  occur  in  the  archipelago.  Hence 
we  may  safely  infer  that  icebergs  formerly  landed  their 
rocky  burdens  on  the  shores  of  these  mid-ocean  islands, 
and  it  is  at  least  possible  that  they  may  have  brought 
thither  some  few  seeds  of  northern  plants. 

Considering  that  these  several  means  of  transport,  and 
that  other  means,  which  without  doubt  remain  to  be  dis¬ 
covered,  have  been  in  action  year  after  year  for  tens  of 
thousands  of  years,  it  would,  I  think,  be  a  marvelous  fact 
if  many  plants  had  not  thus  become  widely  transported. 
These  means  of  transport  are  sometimes  called  accidental, 
but  this  is  not  strictly  correct :  the  currents  of  the  sea  are 
not  accidental,  nor  is  the  direction  of  prevalent  gales  of 
wind.  It  should  be  observed  that  scarcely  any  means  of 
transport  would  carry  seeds  for  very  great  distances:  for 
seeds  do  not  retain  their  vitality  when  exposed  for  a  great 
length  of  time  to  the  action  of  sea  water;  nor  could  they 
be  long  carried  in  the  crops  or  intestines  of  birds.  These 
means,  however,  would  suffice  for  occasional  transport 
across  tracts  of  sea  some  hundred  miles  in  breadth,  or  from 
island  to  island,  cr  from  a  continent  to  a  neighboring 


MEANS  OF  DISPERSAL.  3go 

island,  but  not  from  one  distant  continent  to  another. 
X'he  floias  of  distant  continents  would  not  by  such  means 
become  mingled;  but  would  remain  as  distinct  as  they  now 
are.  The  currents,  from  their  course,  would  never  brin-r 
seeds  from  North  America  to  Britain,  though  they  mio-ht 
and  do  biing  seeds  from  the  AVbst  Indies  to  our  western 
shores,  where,  if  not  killed  by  their  very  long  immersion 
in  salt  water,  they  could  not  endure  our  climate.  Almost 
every  year,  one  or  two  land-birds  are  blown  across  the 
whole  Atlantic  Ocean,  from  North  America  to  the  western 
shores  of  Ireland  and  England;  but  seeds  could  be  trans¬ 
ported  by  these  rare  wanderers  only  by  one  means,  namely 
by  dirt  adhering  to  their  feet  or  beaks,  which  is  in  itself  a 
rare  accident.  Even  in  this  case,  how  small  would  be  the 
chance  of  a  seed  falling  on  favorable  soil,  and  coming  to 
maturity!  But  it  would  be  a  great  error  to  argue  that 
because  a  well-stocked  island,  like  Great  Britain,  has  not, 
as  far  as  is  known  (and  it  would  be  very  difficult  to  prove 
this),  received  within  the  last  few  centuries,  through  occa¬ 
sional  means  of  transport,  immigrants  from  Europe  or  any 
other,  continent,  that  a  poorly-stocked  island,  though 
standing  more  remote  from  the  mainland,  would  not 
. .  ,  .  _  similai  means.  Out  of  a  hundred 

kinds  of  seeds  01  animals  transported  to  an  island,  even  if 
far  less  well-stacked  than  Britain,  perhaps  not  more  than 
one  would  be  so  well  fitted  to  its  new  home,  as  to  become 
naturalized.  But  this  is  no  valid  argument  against  what 
would  be  effected  by  occasional  means  of  transport, 
during  the  long  lapse  of  geological  time,  while  the  island 
was  being  upheaved,  and  before  it  had  become  fully  stocked 
with  inhabitants.  On  almost  bare  land,  with  few  or  no 
destiuctive  insects  or  birds  living  there,  nearly  every  seed 
which  chanced  to  arrive,  if  fitted  for  the  climate,  would 
germinate  and  survive. 

DISPERSAL  DURING  THE  GLACIAL  PERIOEk 


The  identity  of  many  plants  and  animals,  on  mountain- 
summits,  separated  from  each  other  bv  hundreds  of  miles  of 
lowlands,  where  Alpine  species  could*'  not  possibly  exist,  is 
one  of  the  most  striking  cases  known  of  the  same  species 
Imng  at  distant  points,  without  the  apparent  possibility 


390 


DISPERSAL  DURING 


of  their  having  migrated  from  one  point  to  the  other.  It 
is  indeed  a  remarkable  fact  to  see  so  many  plants  of  the 
same  species  living  on  the  snowy  regions  of  the  Alps  or 
Py  renees,  and  in  the  extreme  northern  parts  of  Europe; 
but  it  is  far  more  remarkable,  that  the  plants  on  the  White 
Mountains,  in  the  United  States  of  America,  are  all  the 
same  with  those  of  Labrador,  and  nearly  all  the  same,  as 
we  hear  from  Asa  Gray,  with  those  on  the  loftiest  mount¬ 
ains  of  Europe.  Even  as  long  ago  as  1747,  such  facts  led 
Gmelin  to  conclude  that  the  same  species  must  have  been 
independently  created  at  many  distinct  points;  and  we 
might  have  remained  in  this  same  belief,  had  not  Agassiz 
and  others  called  vivid  attention  to  the  Glacial  period, 
which,  as  we  shall  immediately  see,  atfords  a  simple  expla¬ 
nation  of  these  facts.  We  have  evidence  of  almost  every 
conceivable  kind,  organic  and  inorganic,  that,  within  a 
very  recent  geological  period,  central  Europe  and  North 
America  suffered  under  an  arctic  climate.  The  ruins  of  a 
house  burned  by  fire  do  not  tell  their  tale  more  plainly  than 
do  the  mountains  of  Scotland  and  Wales,  with  their  scored 
flanks,  polished  surfaces,  and  perched  bowlders,  of  the  icy 
streams  with  which  their  valleys  were  lately  filled.  So 
greatly  has  the  climate  of  Europe  changed,  that  in  North¬ 
ern  Italy,  gigantic  moraines,  left  by  old  glaciers,  are  now 
clothed  by  the  vine  and  maize.  Throughout  a  large  part 
of  the  United  States,  erratic  bowlders  and  scored  rocks 
plainly  reveal  a  former  cold  period. 

The  former  influence  of  the  glacial  climate  on  the  dis¬ 
tribution  of  the  inhabitants  of  Europe,  as  explained  by 
Edward  Forbes,  is  substantially  as  follows.  But  we  shall 
follow  the  changes  more  readily,  by  supposing  a  new  glacial 
period  slowly  to  come  on,  and  then  pass  awa}T,  as  formerly 
occurred.  As  the  cold  came  on,  and  as  each  more  south¬ 
ern  zone  became  fitted  for  the  inhabitants  of  the  north, 
these  would  take  the  places  of  the  former  inhabitants  of 
the  temperate  regions.  The  latter,  at  the  same  time, 
would  travel  further  and  further  southward,  unless  they 
were  stopped  by  barriers,  in  which  case  they  would  perish. 
The  mountains  would  become  covered  with  snow  and  ice, 
and  their  former  Alpine  inhabitants  would  descend  to  the 
plains.  By  the  time  that  the  cold  had  reached  its  maxi¬ 
mum,  we  should  have  an  arctic  fauna  and  flora,  covering 


THE  GLACIAL  PERIOD . 


391 


the  central  parts  of  Europe,  as  far  south  as  the  Alps  and 
Pyrenees,  and  even  stretching  into  Spain.  The  now 
temperate  regions  of  the  United  States  would  likewise  be 
covered  by  arctic  plants  and  animals  and  these  would  be 
nearly  the  same  with  those  of  Europe;  for  the  present 
circumpolar  inhabitants,  which  we  suppose  to  have  every¬ 
where  traveled  southward,  are  remarkably  uniform  round 
the  world. 

As  the  warmth  returned,  the  arctic  forms  would  retreat 
northward,  closely  followed  up  in  their  retreat  by  the  pro¬ 
ductions  of  the  more  temperate  regions.  And  as  the  snow 
melted  from  the  bases  of  the  mountains,  the  arctic  forms 
would  seize  on  the  cleared  and  thawed  ground,  always 
ascending,  as  the  warmth  increased  and  the  snow  still 
further  disappeared,  higher  and  higher,  while  their  breth¬ 
ren  were  pursuing  their  northern  journey.  Hence,  when 
the  warmth  had  fully  returned,  the  same  species,  which 
had  lately  lived  together  on  the  European  and  North 
American  lowlands,  would  again  be  found  in  the  arctic 
regions  of  the  Old  and  New  Worlds,  and  on  many  isolated 
mountain  summits  far  distant  from  each  other. 

Thus  we  can  understand  the  identity  of  many  plants  at 
points  so  immensely  remote  as  the  mountains  of  the  United 
States  and  those  of  Europe.  We  can  thus  also  understand 
the  fact  that  the  Alpine  plants  of  each  mountain-range  are 
more  especially  related  to  the  arctic  forms  living  due 
north  or  nearly  due  north  of  them:  for  the  first  migration 
when  the  cold  came  on,  and  the  re-migration  on  the  return¬ 
ing  warmth,  would  generally  have  been  due  south  and 
north.  The  Alpine  plants,  for  example,  of  Scotland,  as 
remarked  by  Mr.  H.  0.  Watson,  and  those  of  the  Pyrenees, 
as  remarked  by  Ramond,  are  more  especially  allied  to  the 
plants  of  northern  Scandinavia;  those  of  the  United 
States  to  Labrador;  those  of  the  mountains  of  Siberia  to 
the  arctic  regions  of  that  country.  These  views,  grounded 
as  they  are  on  the  perfectly  well-ascertained  occurrence  of  a 
former  Glacial  period,  seem  to  me  to  explain  in  so  satis¬ 
factory  a  manner  the  present  distribution  of  the  Alpine 
and  Arctic  productions  of  Europe  and  America,  that  when 
in  other  regions  we  find  the  same  species  on  distant  mount¬ 
ain-summits,  we  may  almost  conclude,  without  other 
evidence,  that  a  colder  climate  formerly  permitted  their 


392 


DISPERSAL  DURING 


migration  across  the  intervening  lowlands,  now  become 
too  warm  for  their  existence. 

As  the  arctic  forms  moved  first  southward  and  after- 
waid  backward  to  the  north,  in  unison  with  the  changin0, 
climate,  they  will  not  have  been  exposed  during  their  long 
migrations  to  any  great  diversity  of  temperature;  and  as 
they  all  migrated  in  a  body  together,  their  mutual  rela¬ 
tions  will  not  have  been .  much  disturbed.  Hence,  in 
accoi dance  with  the  principles  inculcated  in  this  volume, 
these  forms  will  not  have  been  liable  to  much  modification. 
But  with  the  Alpine  productions,  left  isolated  from  the 
moment  of  the  returning  warmth,  first  at  the  bases  and 
ultimately  on  the  summits  of  the  mountains,  the  case  will 
have  been  soniewhat  different;  for  it  is  not  likely  that  all 
the  same  arctic  species  will  have  been  left  on  mountain 
ranges  far  distant  from  each  other,  and  have  survived  there 
ever  since;  they  will  also,  in  all  probability,  have  become 
mingled  with  ancient  Alpine  species,  which  must  have 
existed  on  the  mountains  before  the  commencement  of  the 
Glacial  epoch,  and  which  during  the  coldest  period  will 
have  been  temporarily  driven  down  to  the  plains;  they 
will,  also,  have  been  subsequently  exposed  to  somewhat 
dilfeient  climatical  influences.  Their  mutual  relations  will 
thus  have  been  in  some  degree  disturbed;  consequently 
they  will  have  been  liable  to  modification;  and  they  have 
been  modified;  for  if  we  compare  the  present  Alpine  plants 
and  animals  of  the  several  great  European  mountain 
1  anges,  one  with  another,  though  many  of  the  species 
remain  identically  the  same,  some  exist  as  varieties,  some 
as  doubtful  forms  or  sub-species  and  some  as  distinct  yet 

closely  allied  species  representing  each  other  on  the  several 
ranges. 

In  the  foregoing  illustration  I  have  assumed  that  at  the 
commencement  of  our  imaginary  Glacial  period,  the  arctic 
piod actions  were  as  uniform  round  the  polar  regions  as 
they  aie  at  the  present  da}7.  But  it  is  also  necessary  to 
assume  that  many  sub-arctic  and  some  few  temperate  forms 
were  the  same  round  the  world,  for  some  of  the  species 
which  now  exist  on  the  lower  mountain  slopes  and  on  the 
plains  of  North  America  and  Europe  are  the  same;  and  it 
nia\  be  asked  how  I  account  for  this  degree  of  uniformity 
in  the  sub-arctic  and  temperate  forms  round  the  world,  at 


THE  GLACIAL  PERIOD.  393 

the  commencement  of  the  real  Glacial  period.  At  the 
present  day  the  sub-arctic  and  northern  temperate  pro¬ 
ductions  of  the  Old  and  New  Worlds  are  separated  from 
each  other  by  the  whole  Atlantic  Ocean  and  by  the  north¬ 
ern  part  of  the  Pacific.  During  the  Glacial  period,  when 
the  inhabitants  of  the  Old  and  New  Worlds  lived  further 
southward  then  they  do  at  present,  they  must  have  been 
still  more  completely  separated  from  each  other  by  wider 
spaces  of  ocean;  so  that  it  may  well  be  asked  how  the  same 
species  could  then  or  previously  have  entered  the  two  con¬ 
tinents.  The  explanation,  I  believe,  lies  in  the  nature  of 
the  climate  before  the  commencement  of  the  Glacial  period 
At  tins,  the  newer  Pliocene  period,  the  majority  of  the  in¬ 
habitants  of  the  world  were  specifically  the  same  as  now,  and 
we  have  good  reason  to  believe  that  the  climate  was  warmer 
than  at  the  present  day.  Hence,  we  may  suppose  that  the 
organisms  which  now  live  under  latitude  60  degrees,  lived 
during  the  Pliocene  period  further  north,  under  the  Polar 
Circle,  m  latitude  66-67  degrees;  and  that  the  present  arctic 
productions  then  lived  on  the  broken  land  still  nearer  to  the 
P°le‘  ^  w®  look  at  a  terrestrial  globe,  we  see  under 

the  Polar  Circle  that  there  is  almost  continuous  land  from 
western  Europe  through  Siberia,  to  eastern  America.  And 
this  continuity  of  the  circumpolar  land,  with  the  conse¬ 
quent  freedom  under  a  more  favorable  climate  for  inter- 
migration,  will  account  for  the  supposed  uniformity  of  the 
sub-arctm  and  temperate  productions  of  the  Old  and  New 
*  or  Ids,  at  a  period  anterior  to  the  Glacial  epoch. 

Believing,  from  reasons  before  alluded  to,  that  our  con¬ 
tinents  have  long  remained  in  nearly  the  same  relative 
position,  though  subjected  to  great  oscillations  of  level,  I 
am  strongly  inclined  to  extend  the  above  view,  and  to  infer 
that  during  some  still  earlier  and  still  warmer  period,  such 
as  the  older  Pliocene  period,  a  large  number  of  the  same 
plants  and  animals  inhabited  the  almost  continuous  cir- 

an^_tkat  these  plants  and  animals,  both  in 
the  Old  and  New  Worlds,  begun  slowly  to  migrate  south¬ 
ward  as  the  climate  became  less  warm,  long  before  the 
commencement  of  the  Glacial  period.  We  now  see,  as  I 
believe,  their  descendants,  mostly  in  a  modified  condition, 
m  the  central  parts  of  Europe  and  the  United  States.  On 
this  view  we  can  understand  the  relationship  with  very 


DISPERSAL  DURING 


394 


little  identity,  between  the  productions  of  North  America 
and  Europe — a  relationship  which  is  highly  remarkable, 
considering  the  distance  of  the  two  areas,  and  theii  sepa¬ 
ration  by  the  whole  Atlantic  Ocean.  We  can  further  under¬ 
stand  the  singular  fact  remarked  on  by  several  observers 
that  the  productions  of  Europe  and  America  dining  the 
later  tertiary  stages  were  more  closely  related  to  each  other 
than  they  are  at  the  present  time;  for  during  these  warmer 
periods  the  northern  parts  of  the  Old  and  New  Worlds  will 
have  been  almost  continuously  united  by  land,  serving  as  a 
bridge,  since  rendered  impassible  by  cold,  for  intermigra¬ 
tion  of  their  inhabitants.  . 

During  the  slowly  decreasing  warmth  of  the  Pliocene 
period,  as  soon  as  the  species  in  common,  which  inhabited 
the  New  and  Old  Worlds,  migrated  south  of  the  Polar  Circle, 
they  will  have  been  completely  cut  off  from  each  other. 
This  separation,  as  far  as  the  more  temperate  productions 
are  concerned,  must  have  taken  place  long  ages  ago.  As 
the  plants  and  animals  migrated  southward,  they  will 
have*  become  mingled  in  the  one  great  region  with  the 
native  American  productions,  and  would  have  had  to  com¬ 
pete  with  them;  and  in  the  other  great  region,  with  those 
of  the  Old  World.  Consequently  we  have  here  everything 
favorable  for  much  modification— for  far  more  modifica¬ 
tion  than  with  the  Alpine  productions,  left  isolated,  within 
a  much  more  recent  period,  on  the  several  mountain  ranges 
and  on  the  arctic  lands  of  Europe  and  North  America.  Hence, 
it  has  come,  that  when  we  compare  the  now  living  produc¬ 
tions  of  the  temperate  regions  of  the  New  and  Old  Worlds, 
we  find  very  few  identical  species  (though  Asa  Gray  has 
lately  shown  that  more  plants  are  identical  than  was  for¬ 
merly  supposed),  but  we  find  in  every  great  class  many 
forms,  which  some  naturalists  rank  as  geographical  laces, 
and  others  as  distinct  species;  and  a  host  of  closely  allied 
or  representative  forms  which  are  ranked  by  all  naturalists 
as  specifically  distinct. 

As  on  the  land,  so  in  the  waters  of  the  sea,  a  slow  south¬ 
ern  migration  of  a  marine  fauna,  which,  during  the  Pliocene 
or  even  a  somewhat  earlier  period,  was  nearly  uniform  along 
the  continuous  shores  of  the  Polar  Circle,  will  account,  on 
the  theory  of  modification,  for  many  closely  allied  forms 
now  living  in  marine  areas  completely  sundered.  Thus,  1 


TEE  GLACIAL  PERIOD.  395 

think,  we  can  understand,  the  presence  of  some  closely 
allied,  still  existing  and  extinct  tertiary  forms,  on  the 
eastern  and  western  shores  of  temperate  North  America; 
and  the  still  more  striking  fact  of  many  closely  allied  crus¬ 
taceans  (as  described  in  Dana’s  admirable  work),  some  fish 
and  other  marine  animals,  inhabiting  the  Mediterranean 
and  the  seas  of  Japan — these  two  areas  being  now  com¬ 
pletely  separated  by  the  breadth  of  a  whole  continent  and 
by  wide  spaces  of  ocean. 

These  cases  of  close  relationship  in  species  either  now  or 
formerly  inhabiting  the  seas  on  the  eastern  and  western 
shores  of  North  America,  the  Mediterranean  and  Japan, 
and  the  temperate  lands  of  North  America  and  Europe, 
are.  inexplicable  on  the  theory  of  creation.  We  cannot 
maintain  that  such  species  have  been  created  alike,  in  cor¬ 
respondence  with  the  nearly  similar  physical  conditions  of 
the  areas;  for  if  we  compare,  for  instance,  certain  parts  of 
South  America  with  parts  of  South  Africa  or  Australia,  we 
see  countries  closely  similar  in  all  their  physical  conditions 
with  their  inhabitants  utterly  dissimilar. 

ALTERNATE  GLACIAL  PERIODS  IN  THE  NORTH  AND  SOUTH. 

But  we  must  return  to  our  more  immediate  subject.  I 
am  convinced  that  Eorbes’  view  may  be  largely  extended. 
In  Europe  we  meet  with  the  plainest  evidence  of  the  Glacial 
period,  from  the  western  shores  of  Britain  to  the  Ural 
range,  and  southward  to  the  Pyrenees.  We  may  infer 
from  the  frozen  manimals  and  nature  of  the  mountain 
vegetation,  that  Siberia  was  similarly  affected.  In  the  Leb¬ 
anon,  according  to  Dr.  Hooker,  perpetual  snow  formerly 
coveied  the  central  axis,  and  fed  glaciers  which  rolled 
4,000  feet  down  the  valleys.  The  same  observer  has 
recently  found  great. moraines  at  a  low  level  on  the  Atlas 
range  in  North  Africa.  Along  the  Himalaya,  at  points 
900  miles  apart,  glaciers  have  left  the  marks  of  their 
foimer  low  descent;  and  in  Sikkim,  Dr.  Hooker  saw  maize 
growing  on  ancient  and  gigantic  moraines.  Southward  of 
the  Asiatic  continent,  on  the  opposite  side  of  the  equator, 
we  know,  from  the  excellent  researches  of  Dr.  J.  Haast 
and  Di.  Hector,  that  in  New  Zealand  immense  glaciers 
foimeily  descended  to  a  low  level;  and  the  same  plants 


39G 


ALTERNATE  GLACIAL  PERIODS 


found  by  Dr.  Hooker  on  widely  separated  mountains  in 
this  island  tell  the  same  story  of  a  former  cold  period. 
From  facts  communicated  to  me  by  the  Rev.  W.  B. 
Clarke,  it  appears  also  that  there  are  traces  of  former  gla¬ 
cial  action  on  the  mountains  of  the  south-eastern  corner 
of  Australia. 

Looking-  to  America;  in  the  northern  half,  ice-borne 
fragments  of  rock  have  been  observed  on  the  eastern  side 
of  the  continent,  as  far  south  as  latitude  thirty-six  and 
thirty-seven  degrees,  and  on  the  shores  of  the  Pacific, 
where  the  climate  is  now  so  different,  as  far  south  as  lati¬ 
tude  forty-six  degrees.  Erratic  bowlders  have,  also,  been 
noticed  on  the  Rocky  Mountains.  In  the  Cordillera  of 
South  America,  nearly  under  the  equator,  glaciers  once 
extended  far  below  their  present  level.  In  Central  Chili  I 
examined  a  vast  mound  of  detritus  with  great  bowlders, 
crossing  the  Portillo  valley,  which,  there  can  hardly  be  a 
doubt,  once  formed  a  huge  moraine;  and  Mr.  D.  Forbes 
informs  me  that  he  found  in  various  parts  of  the  Cordillera, 
from  latitude  thirteen  to  thirty  degrees  south,  at  about  the 
height  of  12,000  feet,  deeply-furrowed  rocks,  resembling 
those  with  which  he  was  familiar  in  Norway,  and  likewise 
great  masses  of  detritus,  including  grooved  pebbles.  Along 
this  whole  space  of  the  Cordillera  true  glaciers  do  not  now 
exist  even  at  much  more  considerable  heights.  Further 
south,  on  both  sides  of  the  continent,  from  latitude  forty- 
one  degrees  to  the  southernmost  extremity,  we  have  the 
clearest  evidence  of  former  glacial  action,  in  numerous 
immense  bowlders  transported  far  from  their  parent 
source. 

From  these  several  facts,  namely,  from  the  glacial  action 
having  extended  all  round  the  northern  and  southern 
hemispheres — from  the  period  having  been  in  a  geological 
sense  recent  in  both  hemispheres — from  its  having  lasted 
in  both  during  a  great  length  of  time,  as  may  be  inferred 
from  the  amount  of  work  effected — and  lastly,  from  gla¬ 
ciers  having  recently  descended  to  a  low  level  along  the 
whole  line  of  the  Cordillera,  it  at  one  time  appeared  to  me 
that  we  could  not  avoid  the  conclusion  that  the  tempera¬ 
ture  of  the  whole  world  had  been  simultaneously  lowered 
during  the  Glacial  period.  But  now,  Mr.  Croll,  in  a  series 
of  admirable  memoirs,  has  attempted  to  show  that  a  glacial 


IN  THE  NORTH  AND  SOUTH 


39? 


condition  of  climate  is  the  result  of  various  physical  causes, 
brought  into  operation  by  an  increase  in  the  eccentricity  of 
the  earth's  orbit.  All  these  causes  tend  toward  the  same 
end;  but  the  most  powerful  appears  to  be  the  indirect  in¬ 
fluence  of  the  eccentricity  of  the  orbit  upon  oceanic  cur- 
lents.  According  to  Mr.  Croll,  cold  periods  regularly  recur 
every  ten  or  fifteen  thousand  years;  and  these  at  long  in- 
teivals  aie  extremely  severe,  owing  to  certain  contingen¬ 
cies,  of  which  the  most  important,  as  Sir  0.  Lyell  has 
shown,  is  the  relative  position  of  the  land  and  water.  Mr. 
Croll  believes  that  the  last  great  glacial  period  occurred 
about  240,000  years  ago,  and  endured,  with  slight  altera¬ 
tions  of  climate,  for  about  160,000  years.  With  respect  to 
moie  ancient  glacial  periods,  several  geologists  are  con¬ 
vinced,  from  direct  evidence,  that  such  occurred  during  the 
miocene  and  eocene  formations,  not  to  mention  still  more 
ancient  formations.  But  the  most  important  result  for  us, 
anived  at  by  Mr.  Croll,  is  that  whenever  the  northern 
hemisphere  passes  through  a  cold  period  the  temperature 
of  the  southern  hemisphere  is  actually  raised,  with  the 
winters  rendered  much  milder,  chiefly  through  changes  in 
the  direction  of  the  ocean  currents.  So  conversely  it  will 
be  with  the  northern  hemisphere,  while  the  southern  passes 
through  a  glacial  period.  This  conclusion  throws  so  much 
light  on  geographical  distribution  that  I  am  strongly  in¬ 
clined  to  trust  in  it;  but  I  will  first  give  the  facts  which 
demand  an  explanation. 

In  South  America,  Dr.  Hooker  has  shown  that  besides 
many  closely  allied  species,  between  forty  and  fifty  of  the 
flowering  plants  of  Tierra  del  Fuego,  forming  no  inconsid¬ 
erable.  part  of  its  scanty  flora,  are  common  to  North 
America  and  Europe,  enormously  remote  as  these  areas  in 
opposite  hemispheres  are  from  each  other.  On  the  lofty 
mountains  of  equatorial  America  a  host  of  peculiar  species 
belonging  to  European  genera  occur.  On  the  Organ 
Mountains  of  Brazil  some  few  temperate  European,  some 
Antarctic  and  some  Andean  genera  wrere  found  by  Gardner 
which  do  not  exist  in  the  low  intervening  hot  countries. 
On  the  Silla  of  Caraccas  the  illustrious  Humboldt  long  ago 
found  species  belonging  to  genera  characteristic  of  the 
Cordillera. 

In  Africa,  several  forms  characteristic  of  Europe,  and 


398 


ALTERNATE  GLACIAL  PERIODS 


some  few  representatives  of  the  flora  of  the  Cape  of 
Good  Hope,  occur  on  the  mountains  of  Abyssinia.  At 
the  Cape  of  Good  Hope  a  very  few  European  species, 
believed  not  to  have  been  introduced  by  man,  and  on  the 
mountains  several  representative  European  forms  are  found 
which  have  not  been  discovered  in  the  intertropical  parts 
of  Africa.  Dr.  Hooker  has  also  lately  shown  that  several 
of  the  plants  living  on  the  upper  parts  of  the  lofty  island 
of  Fernando  Po,  and  on  the  neighboring  Cameroon  Mount¬ 
ains,  in  the  Gulf  of  Guinea,  are  closely  related  to  those  on 
the  mountains  of  Abyssinia,  and  likewise  to  those  of  tem¬ 
perate  Europe.  It  now  also  appears,  as  I  hear  from  Hr. 
Hooker,  that  some  of  these  same  temperate  plants  have 
been  discovered  by  the  Rev.  R.  T.  Lowe  on  the  mountains 
of  the  Cape  Verde  Islands.  This  extension  of  the  same  tem¬ 
perate  forms,  almost  under  the  equator,  across  the  whole 
continent  of  Africa  and  to  the  mountainsof  the  Cape  Verde 
archipelago,  is  one  of  the  most  astonishing  facts  ever  re¬ 
corded  in  the  distribution  of  plants. 

On  the  Himalaya,  and  on  the  isolated  mountain  ranges 
of  the  peninsula  of  India,  on  the  heights  of  Ceylon  and  op 
the  volcanic  cones  of  Java,  many  plants  occur  either  identi¬ 
cally  the  same  or  representing  each  other,  and  at  the  same 
time  representing  plants  of  Europe  not  found  in  the  inter¬ 
vening  hot  lowlands.  A  list  of  the  genera  of ^  plants  col¬ 
lected  on  the  loftier  peaks  of  .Java,  raises  a  picture  of  a 
collection  made  on  a  hillock  in  Europe.  Still  more  strik¬ 
ing  is  the  fact  that  peculiar  Australian  forms  are  repre¬ 
sented  by  certain  plants  growing  on  the  summits  of  the 
mountains  of  Borneo.  Some  of  these  Australian  forms,  as 
I  hear  from  Dr.  Hooker,  extend  along  the  heights  of  the 
peninsula  of  Malacca,  and  are  thinly  scattered  on  the  one 
hand  over  India,  and  on  the  other  hand  as  far  north  as 
Japan. 

On  the  southern  mountains  of  Australia,  Dr.  F.  Muller 
has  discovered  several  European  species;  other  species, 
not  introduced  by  man,  occur  on  the  lowlands;  and  a  long 
list  can  be  given,  as  I  am  informed  by  Dr.  Hooker,  of 
European  genera,  found  in  Australia,  but  not  in  the  inter¬ 
mediate  torrid  regions.  In  the  admirable  “Introduction 
to  the  Flora  of  New  Zealand,”  by  Dr.  Hooker,  analogous 
and  striking  facts  are  given  in  regard  to  the  plants  of  that 


IN  THE  NORTH  AND  SOUTH . 


399 


large  island.  Hence,  we  see  that  certain  plants  growing  on 
the  more  lofty  mountains  of  the  tropics  in  all  parts  of  the 
world,  and  on  the  temperate  plains  of  the  north  and  south, 
are  either  the  same  species  or  varieties  of  the  same  species. 
It  should,  however,  be  observed  that  these  plants  are  not 
strictly  arctic  forms;  for,  as  Mr.  H.  0.  Watson  has  re¬ 
marked,  “  in  receding  from  polar  toward  equatorial  lati¬ 
tudes,  the  Alpine  or  mountain  flora  really  become  less  and 
less  Arctic."  Besides  these  identical  and  closely  allied 
forms,  many  species  inhabiting  the  same  widely  sundered 
areas,  belong  to  genera  not  now  found  in  the  intermediate 
tropical  lowlands. 

These  brief  remarks  apply  to  plants  alone;  but  some  few 
analogous  facts  could  be  given  in  regard  to  terrestrial 
animals.  In  marine  productions,  similar  cases  likewise 
occur;  as  an  example,  I  may  quote  a  statement  by  the 
highest  authority,  Professor  Dana,  that  “it  is  certainly  a 
wonderful  fact  that  New  Zealand  should  have  a  closer  re¬ 
semblance  in  its  Crustacea  to  Great  Britain,  its  antipode, 
than  to  any  other  part  of  the  world."  Sir  J.  Richardson, 
also,  speaks  of  the  reappearance  on  the  shores  of  New 
Zealand,.  Tasmania,  etc.,  of  northern  forms  of  fish.  Dr. 
Hooker  informs  me  that  twenty-five  species  of  Algge  are 
common  to  New  Zealand  and  to  Europe,  but  have  not 
been  found  in  the  intermediate  tropical  seas. 

From  the  foregoing  facts,  namely,  the  presence  of  tem¬ 
perate  forms  on  the  highlands  across  the  whole  of  equatorial 
Africa,  and  along  the  Peninsula  of  India,  to  Ceylon  and 
the  Malay  Archipelago,  and  in  a  less  well-marked  manner 
across  the  wide  expanse  of  tropical  South  America,  it  ap¬ 
pears  almost  certain  that  at  some  former  period,  no  doubt 
during  the  most  severe  part  of  a  Glacial  period,  the  low¬ 
lands  of  these  great  continents  were  everywhere  tenanted 
under  the  equator  by  a  considerable  number  of  temperate 
forms.  At  this  period  the  equatorial  climate  at  the  level 
of  the  sea  was  probably  about  the  same  with  that  now  ex¬ 
perienced  at  the  height  of  from  five  to  six  thousand  feet 
under  the  same  latitude,  or  perhaps  even  rather  cooler. 
During  this,  the  coldest  period,  the  lowlands  under  the 
equator  must  have  been  clothed  with  a  mingled  tropical 
and  temperate  vegetation,  like  that  described  by  Hooker  as 
growing  luxuriantly  at  the  height  of  from  four  to  five 


400  ALTERNATE  GLACIAL  PERIODS 

thousand  feet  on  the  lower  slopes  of  the  Himalaya,  but 
with  perhaps  a  still  greater  preponderance  of  temperate 
forms.  So  again  in  the  mountainous  island  of  Fernando 
Po,  in  the  Gulf  of  Guinea,  Mr.  Mann  found  temperate 
European  forms  begining  to  appear  at  the  height  of  about 
five  thousand  feet.  On  the  mountains  of  Panama,  at  the 
height  of  only  two  thousand  feet,  Dr.  Seemann  found  the 
vegetation  like  that  of  Mexico,  “  with  forms  of  the  torrid 
zone  harmoniously  blended  with  those  of  the  temper¬ 
ate.” 

Now  let  us  see  whether  Mr.  C roll’s  conclusion  that  when 
the  northern  hemisphere  suffered  from  the  extreme  cold  of 
the  great  Glacial  period,  the  southern  hemisphere  was 
actually  warmer,  throws  any  clear  light  on  the  present  ap¬ 
parently  inexplicable  distribution  of  various  organisms  in 
the  temperate  parts  of  both  hemispheres,  and  on  the 
mountains  of  the  tropics.  The  Glacial  period,  as  measured 
by  years,  must  have  been  very  long;  and  when  we  remem¬ 
ber  over  what  vast  spaces  some  naturalized  plants  and  ani- 
mals  have  spread  within  a  few  centuries,  this  period  will 
have  been  ample  for  any  amount  of  migration.  As  the 
cold  became  more  and  more  intense,  we  know  that  Arctic 
forms  invaded  the  temperate  regions;  and,  from  the  facts 
-just  given,  there  can  hardly  be  a  doubt  that  some  of  the 
more  vigorous,  dominant  and  widest-spreading  temperate 
forms  invaded  the  equatorial  lowlands.  The  inhabitants 
of  these  hot  lowlands  would  at  the  same  time  have  migrated 
to  the  tropical  and  subtropical  regions  of  the  south,  for  the 
southern  hemisphere  was  at  this  period  warmer.  On  the 
decline  of  the  Glacial  period,  as  both  hemispheres  gradu¬ 
ally  recovered  their  former  temperature,  the  northern  tem¬ 
perate  forms  living  on  the  lowlands  under  the  equator, 
would  have  been  driven  to  their  former  homes  or  have  been 
destroyed,  being  replaced  by  the  equatorial  forms  return¬ 
ing  from  the  south.  Some,  however,  of  the  northern 
temperate  forms  would  almost  certainly  have  ascended  any 
adjoining  high  land,  where,  if  sufficiently  lofty,  they  would 
have  long  survived  like  the  Arctic  forms  on  the  mountains 
of  Europe.  They  might  have  survived,  even  if  the  climate 
was  not  perfectly  fitted  for  them,  for  the  change  of  tem¬ 
perature  must  have  been  very  slow,  and.  plants  undoubtedly 
possess  a  certain  capacity  for  acclimatization,  as  shown  by 


IN  THE  NORTH  AND  SOUTH. 


401 


their  transmitting  to  their  offspring  different  constitutional 
powers  of  resisting  heat  and  cold. 

In  the  regular  course  of  events  the  southern  hemisphere 
would  in  its  turn  be  subjected  to  a  severe  Glacial  period, 
with  the  northern  hemisphere  rendered  warmer;  and  then 
the  southern  temperate  forms  would  invade  the  equatorial 
lowlands.  The  northern  forms  which  had  before  been  left 
on  the  mountains  would  now  descend  and  mingle  with  the 
southern  forms.  These  latter,  when  the  warmth  returned, 
would  return  to  their  former  homes,  leaving  some  few 
species  on  the  mountains,  and  carrying  southward  with 
them  some  of  the  northern  temperate  forms  which  had 
descended  from  their  mountain  fastnesses.  Thus,  we 
should  have  some  few  species  identically  the  same  in  the 
northern  and  southern  temperate  zones  and  on  the  mount¬ 
ains  of  the  intermediate  tropical  regions.  But  the  species 
left  during  a  long  time  on  these  mountains,  or  in  opposite 
hemispheres,  would  have  to  compete  with  many  new  forms 
and  would  be  exposed  to  somewhat  different  physical  con¬ 
ditions;  hence,  they  would  be  eminently  liable  to  modifica¬ 
tion,  and  would  generally  now  exist  as  varieties  or  as  rep¬ 
resentative  species;  and  this  is  the  case.  We  must,  also, 
bear  in  mind  the  occurrence  in  both  hemispheres  of  former 
Glacial  periods;  for  these  will  account,  in  accordance  with 
the  same  principles,  for  the  many  quite  distinct  species  in¬ 
habiting  the  same  widely  separated  areas,  and  belonging  to 
genera  not  now  found  in  the  intermediate  torrid  zones. 

It  is  a  remarkable  fact,  strongly  insisted  on  by  Hooker, 
in  regard  to  America,  and  by  Alph.  de  Candolle  in  regard 
to  Australia,  that  many  more  identical  or  slightly  modified 
species  have  migrated  from  the  north  to  the  south,  than  in 
a  reversed  direction.  We  see,  however,  a  few  southern 
forms  on  the  mountains  of  Borneo  and  Abyssinia.  I  sus¬ 
pect  that  this  preponderant  migration  from  the  north  to 
the  south  is  due  to  the  greater  extent  of  land  in  the  north, 
and  to  the  northern  forms  having  existed  in  their  own 
homes  in  greater  numbers,  and  having  consequently  been 
advanced  through  natural  selection  and  competition  to  a 
higher  stage  of  perfection,  or  dominating  power,  than  the 
southern  forms.  And  thus,  when  the  two  sets  became 
commingled  in  the  equatorial  regions,  during  the  alterna¬ 
tions  of  the  Glacial  periods,  the  northern  forms  were  tho 


403 


ALTERNATE  GLACIAL  PERIODS 


more  powerful  and  were  able  to  hold  their  places  on  the 
mountains,  and  afterward  to  migrate  southward  with  the 
southern  forms;  but  not  so  the  southern  in  regard  to  the 
northern  forms.  In  the  same  manner,  at  the  present  day, 
we  see  that  very  many  European  productions  cover  the 
ground  in  La  Plata,  New  Zealand,  and  to  a  lesser  degree 
in  Australia,  and  have  beaten  the  natives;  whereas 
extremely  few  southern  forms  have  become  naturalized  in 
any  part  of  the  northern  hemisphere,  though  hides,  wool, 
and  other  objects  likely  to  carry  seeds  have  been  largely 
imported  into  Europe  during  the  last  two  or  three  cen¬ 
turies  from  La  Plata  and  during  the  last  forty  or  fifty  years 
from  Australia.  The  Neilgherrie  Mountains  in  India, 
however,  offer  a  partial  exception;  for  here,  as  I  hear  from 
Dr.  Hooker,  Australian  forms  are  rapidly  sowing  them¬ 
selves  and  becoming  naturalized.  Before  the  last  great 
Glacial  period,  no  doubt  the  intertropical  mountains  were 
stocked  with  endemic  Alpine  forms;  but  these  have  almost 
everywhere  yielded  to  the  more  dominant  forms  generated 
in  the  larger  areas  and  more  efficient  workshops  of  the 
north.  In  many  islands  the  native  productions  are  nearly 
equalled,  or  even  outnumbered,  by  those  which  have 
become  naturalized;  and  this  is  the  first  stage  toward  their 
extinction.  Mountains  are  islands  on  the  land,  and  their 
inhabitants  have  yielded  to  those  produced  within  the 
larger  areas  of  the  north,  just  in  the  same  way  as  the 
inhabitants  of  real  islands  have  everywhere  yielded  and  are 
still  yielding  to  continental  forms  naturalized  through 
man’s  agency. 

The  same  principles  apply  to  the  distribution  of  terres¬ 
trial  animals  and  of  marine  productions,  in  the  northern 
and  southern  temperate  zones,  and  on  the  intertropical 
mountains.  When,  during  the  height  of  the  Glacial 
period,  the  ocean-currents  were  widely  different  to  what 
they  now  are,  some  of  the  inhabitants  of  the  temperate  seas 
might  have  reached  the  equator;  of  these  a  few  would  per¬ 
haps  at  once  be  able  to  migrate  southward,  by  keeping  to 
the  cooler  currents,  while  others  might  remain  and  sur¬ 
vive  in  the  colder  depths  until  the  southern  hemisphere 
was  in  its  turn  subjected  to  a  glacial  climate  and  permitted 
their  further  progress;  in  nearly  the  same  manner  as, 
according  to  Forbes,  isolated  spaces  inhabited  by  Arctic 


/Ar  T1IE  NORTH  AND  SOUTH.  4o;} 

productions  exist  to  the  present  day  in  the  deeper  parts  of 
the  northern  temperate  seas.  1  1 

1  .T!  f™m.,suPPosin£  that  all  the  difficulties  in 
legard  to  the  distribution  and  affinities  of  the  identical  and 
allied  species,  which  now  live  so  widely  separated  in  the 
north  and  south,  and  sometimes  on  the  intermediate  mount¬ 
ain-!  anges,  are  removed  on  the  views  above  given.  The 
exact  lines  of  migration  cannot  be  indicated.  We  cannot 
say  why  certain  species  and  not  others  have  migrated-  whv 
ceitain  species  have  been  modified  and  have  given  rise  to 
new  forms,  while  others  have  remained  unaltered.  We 
cannot  hope  to  explain  such  facts,  until  we  ?an  say  why 
one  species  and  not  another  becomes  naturalized  by  man's 
agency  in  a  foreign  land;  why  one  species  ranges  twice  or 
thrice  as  tar,  and  is  twice  or  thrice  as  common,  as  another 
species  within  their  own  homes. 

.  Various  special  difficulties  also  remain  to  be  solved*  for 
instance,  the  occurrence,  as  shown  by  Dr.  Hooker,  of  the 
same  plants  at  points  so  enormously  remote  as  Kerguelen 
and,  New  Zealand,  and  Fuegia;  but  icebergs,  as  suggested 
by  Lyell,  may  have  been  concerned  in  their  dispersal.  The 
existence  at  these  and  other  distant  points  of  the  southern 
hemisphere,  of  species,  which,  though  distinct,  belong  to 
genera  exclusively  confined  to  the  south,  is  a  more  remark¬ 
able  case.  Some  of  these  species  are  so  distinct,  that  we 
cannot  suppose  that  there  has  been  time  since  the  com- 
mencement  of  the  last  Glacial  period  for  their  migration 
and  subsequent  modification  to  the  necessary  degree.  The 
acts  seem  to  indicate  that  distinct  species  belonging  to  the 
same  genera  have  migrated  in  radiating  lines  from  a 
common  center;  and  I  am  inclined  to  look  in  the  southern 
as  in  the  northern  hemisphere,  to  a  former  and  warmer 
period,  before  the  commencement  of  the  last  Glacial 
period,  when  the  Antarctic  lands,  now  covered  with  ice 
supported  a  highly  peculiar  and  isolated  flora.  It  may  be 
suspected  that  before  this  flora  was  exterminated  during  the 
last  Glacial  epoch,  a  few  forms  had  been  already  widelv  dis¬ 
persed  to  various  points  of  the  southern  hemisphere  bv  oc¬ 
casional  means  of  transport,  and  by  the  aid,  as  halting- 
places,  of  now  sunken  islands.  Thus  the  southern  shores 
of  America  Australia,  and  New  Zealand  may  have  become 
slightly  tinted  by  the  same  peculiar  forms  of  lifew 


404 


ALTERNATE  GLACIAL  PERIODS. 


Sir  C.  Lyell  in  a  striking  passage  lias  speculated,  in  lan¬ 
guage  almost  identical  with  mine,  on  the  effects  of  great 
alterations  of  climate  throughout  the  world  on  geograph¬ 
ical  distribution.  And  we  have  now  seen  that  Mr.  CrolFs 
conclusion  that  successive  Glacial  periods  in  the  one  hemi¬ 
sphere  coincide  with  warmer  periods  in  the  opposite  hemi¬ 
sphere,  together  with  the  admission  of  the  slow  modifica¬ 
tion  of  species,  explains  a  multitude  of  facts  in  the  distri¬ 
bution  of  the  same  and  of  the  allied  forms  of  life  in  all 
parts  of  the  globe.  The  living  waters  have  flowed  during 
one  period  from  the  north  and  during  another  from  the 
south,  and  in  both  cases  have  reached  the  equator;  but  the 
stream  of  life  has  flowed  with  greater  force  from  the  north 
than  in  the  opposite  direction,  and  has  consequently  more 
freely  inundated  the  south.  As  the  tide  leaves  its  drift  in 
horizontal  lines,  rising  higher’  on  the  shores  where  the  tide 
rises  highest,  so  have  the  living  waters  left  their  living 
drift  on  our  mountain  summits,  in  a  line  gently  rising 
from  the  Arctic  lowlands  to  a  great  altitude  under  the 
equator.  The  various  beings  thus  left  stranded  may  be 
compared  with  savage  races  of  man,  driven  up  and  surviv¬ 
ing  in  the  mountain  fastnesses  of  almost  every  land,  which 
serves  as  a  record,  full  of  interest  to  us,  of  the  former  in¬ 
habitants  of  the  surrounding  lowlands. 


FRESH-WATER  PRODUCTIONS. 


405 


CHAPTER  XIII. 

geographical  distribution — continued . 

Distribution  of  fresb-water  productions  —  On  tbe  inhabitants  of 
oceanic  islands — Absence  of  Batrachians  and  of  terrestrial  Mam¬ 
mals — On  the  relation  of  the  inhabitants  of  islands  to  those  of 
the  nearest  mainlaind — On  colonization  from  the  nearest  source 
with  subsequent  modification — Summary  of  the  last  and  present 
chapter. 


FRESH-WATER  PRODUCTIONS. 

As  lakes  and  river  systems  are  separated  from  each 
other  by  barriers  of  land,  it  might  have  been  thought 
that  fresh-water  productions  would  not  have  ranged  widely 
within  the  same  country,  and  as  the  sea  is  apparently  a 
still  more  formidable  barrier,  that  they  would  never  have 
extended  to  distant  countries.  But  the  case  is  exactly  the 
reverse.  Not  only  have  many  fresh- water  species,  belong¬ 
ing  to  different  classes,  an  enormous  range,  but  allied 
species  prevail  in  a  remarkable  manner  throughout  the 
world.  When  first  collecting  in  the  fresh  waters  of  Brazil, 
I  well  remember  feeling  much  surprise  at  the  similarity  of 
the  fresh-water  insects,  shells,  etc.,  and  at  the  dissimilarity 
of  the  surrounding  terrestrial  beings,  compared  with  those 
of  Britain. 

But  the  wide  ranging  power  of  fresh-water  productions 
can,  I  think,  in  most  cases  be  explained  by  their  having 
become  fitted,  in  a  manner  highly  useful  to  them,  for  short 
and  frequent  migrations  from  pond  to  pond,  or  from 
stream  to  stream,  within  their  own  countries;  and  liability 
to  wide  dispersal  would  follow  from  this  capacity  as  an 
almost  necessary  consequence.  We  can  here  consider  only 
a  few  cases;  of  these,  some  of  the  most  difficult  to  explain 
are  presented  by  fish.  It  was  formerly  believed  that  the 
same  fresh-water  species  never  existed*  on  two  continents 


406 


FRESH-WATER  PRODUCTIONS. 


distant  from  each  other.  But  Dr.  Gunther  has  lately 
shown  that  the  Galaxias  attenuatus  inhabits  Tasmania, 
New  Zealand,  the  Falkland  Islands  and  the  mainland  of 
South  America.  This  is  a  wonderful  case,  and  probably 
indicates  dispersal  from  an  Antarctic  center  during  a 
former  warm  period.  This  case,  however,  is  rendered  in 
some  degree  less  surprising  by  the  species  of  this  genus 
having  the  power  of  crossing  by  some  unknown  means  con¬ 
siderable  spaces  of  open  ocean:  thus  there  is  one  species 
common  to  New  Zealand  and  to  the  Auckland  Islands, 
though  separated  by  a  distance  of  about  230  miles..  On 
the  same  continent  fresh-water  fish  often  range  widely, 
and  as  if  capriciously;  for  in  two  adjoining  river  systems 
some  of  the  species  may  be  the  same  and  some  wholly 
different. 

It  is  probable  that  they  are  occasionally  transported  by 
what  may  be  called  accidental  means.  Thus  fishes  still 
alive  are  not  very  rarely  dropped  at  distant  points  by 
whirlwinds;  and  it  is  known  that  the  ova  retain  their 
vitality  for  a  considerable  time  after  removal  from  the 
water.  Their  dispersal  may,  however,  be  mainly  attribu¬ 
ted  to  changes  in  the  level  of  the  land  within  the  recent 
period,  causing  rivers  to  flow  into  each  other.  Instances, 
also,  could  be  given  of  this  having  occurred  during  floods, 
without  any  change  of  level.  The  wide  differences  of  the 
fish  on  the  opposite  sides  of  most  mountain-ranges,  which 
are  continuous  and  consequently  must,  from  ,  an  early 
period,  have  completely  prevented  the  inosculation  of  the 
river,  systems  on  the  two  sides,  leads  to  the  same  conclu¬ 
sion.  Some  fresh-water  fish  belong  to  very  ancient,  forms, 
and  in  such  cases  there  will  have  been  ample  time  for 
great  geographical  changes,  and  consequently  time  and 
means  for  much  migration.  Moreover,  Dr.  Gunther  has 
recently  been  led  by  several  considerations  to  infer  that 
with  fishes  the  same  forms  have  a  long  endurance.  .  Salt¬ 
water  fish  can  with  care  be  slowly  accustomed  to  live  in 
fresh  water;  and,  according  to  Valenciennes,  there  is 
hardly  a  single  group  of  which  all  the  members  are  con¬ 
fined  to  fresh  water,  so  that  a  marine  species  belonging  to 
a  fresh-water  group  might  travel  far  along  the  shores  of 
the  sea,  and  could,  it  is  probable,  become  adapted  without 
much  difficulty  to  the  fresh  waters  of  a  distant  land. 


FRESH-WATER  PRODUCTIONS. 


407 


Some  species  of  fresh- water  shells  have  very  wide  ranges, 
and  allied  species  which,  on  our  theory,  are  descended  from 
a  common  parent,  and  must  have  proceeded  from  a  single 
source,  prevail  throughout  the  world.  Their  distribution 
at  first  perplexed  me  much,  as  their  ova  are  not  likely  to 
be  transported  by  birds;  and  the  ova,  as  well  as  the  adults, 
are  immediately  killed  by  sea-water.  I  could  not  ever, 
understand  how  some  naturalized  species  have  spread 
rapidly  throughout  the  same  country.  But  two  facts, 
which  I  have  observed — and  many  others  no  doubt  will  be 
discovered— throw  some  light  on  this  subject.  When  ducks 
suddenly  emerge  from  a  pond  covered  with  duck-weed,  I 
have  twice  seen  these  little  plants  adhering  to  their  backs; 
and  it  has  happened  to  me,  in  removing  a  little  duck-weed 
from  one  aquarium  to  another,  that  I  have  unintentionally 
stocked  the  one  with  fresh-water  shells  from  the  other. 
But  another  agency  is  perhaps  more  effectual:  I  suspended 
the  feet  of  a  duck  in  an  aquarium,  where  many  ova  of 
fresh- water  shells  were  hatching;  and  I  found  that  numbers 
of  the  extremely  minute  and  just-hatched  shells  crawled 
on  the  feet,  'and  clung  to  them  so  firmly  that  when  taken 
out  of  the  water  they  could  not  be  jarred  off,  though  at  a 
somewhat  more  advanced  age  they  would  voluntarily  drop 
off.  These  just-hatched  molluscs,  though  aquatic  in  their 
nature,  survived  on  the  duck's  feet,  in  damp  air,  from 
twelve  to  twenty  hours;  and  in  this  length  of  time  a  duck 
or  heron  might  fiy  at  least  six  or  seven  hundred  miles,  and 
if  blown  across  the  sea  to  an  oceanic  island,  or  to  any  other 
distant  point,  would  be  sure  to  alight  on  a  pool  or  rivulet. 
Sir  Charles  Lyell  informs  me  that  a  dytiscus  has  been 
caught  with  an  ancylus  (a  fresh-water  shell  like  a  limpet) 
firmly  adhering  to  it;  and  a  water-beetle  of  the  same  family, 
a  colymbetes,  once  flew  on  board  the  “  Beagle;"  when  forty- 
five  miles  distant  from  the  nearest  land:  how  much  farther 
it  might  have  been  blown  by  a  favoring  gale  no  one  can 
tell. 

With  respect  to  plants,  it  has  long  been  known  what 
enormous  ranges  many  fresh-water,  and  even  marsh  species, 
have,  both  over  continents  and  to  the  most  remote  oceanic 
islands.  This  is  strikingly  illustrated,  according  to  Alph. 
de  Candolle,  in  those  large  groups  of  terrestrial  plants, 
which  have  very  few  aquatic  members;  for  the  latter  seem 


408  FRESH-WAT^Tt  PRODtC~tlDff& 

immediately  to  acquire,  as  if  in  consequence,  a  wido 
range.  I  think  favorable  means  of  dispersal  explain 
this  fact.  I  have  before  mentioned  that  earth  occa- 
tionally  adheres  in  some  quantity  to  the  feet  and  beaks 
of  birds.  Wading  birds,  which  frequent  the  muddy  edges 
of  ponds,  if  suddenly  flushed,  would  be  the  most  likely  to 
have  muddy  feet.  Birds  of  this  order  wander  more  than 
those  of  any  other;  and  they  are  occasionally  found  on  the 
most  remote  and  barren  islands  of  the  open  ocean;  they 
would  not  he  likely  to  alight  _  on  the  surface  of  the 
sea,  so  that  any  dirt  on  their  feet  would  not  be 
washed  off;  and  when  gaining  the  land,  they  would  be  sure 
to  fly  to  their  natural  fresh-water  haunts.  I  do  not  believe 
that  botanists  are  aware  how  charged  the  mud  of  ponds  is 
with  seeds;  I  have  tried  several  little  experiments,  but  will 
here  o-ive  only  the  most  striking  case:  I  took  in  February 
three  tablespoonfuls  of  mud  from  three  different  points, 
beneath  water,  on  the  edge  of  a  little  pond;  this  mud  when 
dried  weighed  only  six  and  three-fourth  ounces;  I  kept  it 
covered  up  in  my  study  for  six  months,  pulling  up  and 
counting  each  plant  as  it  grew;  the  plants  weie  of  many 
kinds,  and  were  altogether  537  in  number;  and  yet  the 
viscid  mud  was  all  contained  in  a  breakfast  cup!  Consider¬ 
ing  these  facts,  I  think  it  would  be  an  inexplicable  cir¬ 
cumstance  if  water  birds  did  not  transport  the  seeds  of 
fresh-water  plants  to  unstocked  ponds  and  streams,  situated 
at  verv  distant  points.  The  same  agency  may  have  come 
into  play  with  the  eggs  of  some  of  the  smaller  fresh-water 

animals.  #  . 

Other  and  unknown  agencies  probably  have  also  played 
.  a  part.  I  have  stated  that  fresh-water  fish  eat  some  kind? 
of  seeds,  though  they  reject  many  other  kinds  after  having 
swallowed  them;  even  small  fish  swallow  seeds  of  moderate 
size,  as  of  the  yellow  water-lily  and  Potamogeton.  Herons 
and  other  birds,  century  after  century,  have  gone  on  daily 
devouring  fish;  they  then  take  flight  and  go  to  other 
waters,  or  are  blown  across  the  sea;  and  we  have  seen  that 
seeds  retain  their  power  of  germination,  when  rejected 
many  hours  afterward  in  pellets  or  in  the  excrement. 
When  I  saw  the  great  size  of  the  seeds  of  that  fine  water- 
lily,  the  Nelumbium,  and  remembered  Alph.de  Candolle's 
remarks  on  the  distribution  of  this  plant,  I  thought  that 


INHABITANTS  OF  OCEANIC  ISLANDS. 


409 


the  means  of  its  dispersal  must  remain  inexplicable;  but 
Audubon  statesthat  he  found  the  seeds  of  the  great  southern 
water-lily  (probably  according  to  Dr.  Hooker,  the  Nelumt 
bium  luteum)  in  a  heron's  stomach.  Now  this  bird  mus- 
often  have  flown  with  its  stomach  thus  well  stocked  to  dis¬ 
tant  ponds,  and,  then  getting  a  hearty  meal  of  fish,  \ 
analogy  makes  me  believe  that  it  would  have  rejected  the 
seeds  in  the  pellet  in  a  fit  state  for  germination. 

In  considering  these  several  means  of  distribution,  it 
should  be  remembered  that  when  a  pond  or  stream  is  first 
formed,  for  instance  on  a  rising  islet,  it  will  be  unoccupied; 
and  a  single  seed  or  egg  will  have  a  good  chance  of  succeed¬ 
ing.  Although  there  will  always  be  a  struggle  for  life  be¬ 
tween  the  inhabitants  of  the  same  pond,  however  few  in 
kind,  yet  as  the  number  even  in  a  well-stocked  pond  is  small 
in  comparison  with  the  number  of  sj)ecies  inhabiting  an 
equal  area  of  land,  the  competition  between  them  will  proba¬ 
bly  be  less  severe  than  between  terrestrial  species;  conse¬ 
quently  an  intruder  from  the  waters  of  a  foreign  country 
would  have  a  better  chance  of  seizing  on  a  new  place,  than 
in  the  case  of  terrestrial  colonists.  We  should  also  re¬ 
member  that  many  fresh-water  productions  are  low  in  the 
scale  of  nature,  and  we  have  reason  to  believe  that  such 
beings  become  modified  more  slowly  than  the  high; 
and  this  will  give  time  for  the  migration  of  aquatic  species. 
We  should  not  forget  the  probability  of  many  fresh -water 
forms  having  formerly  ranged  continuously  over  immense 
areas,  and  then  having  become  extinct  at  intermediate 
points.  But  the  wide  distribution  of  fresh-water  plants, 
and  of  the  lower  animals,  whether  retaining  the  same 
identical  form,  or  in  some  degree  modified,  apparently 
depends  in  main  part  on  the  wide  dispersal  of  their  seeds 
and  eggs  by  animals,  more  especially  by  fresh-water  birds,  / 
which  have  great  powers  of  flight,  and  naturally  travel 
from  one  piece  of  water  to  another. 

ON"  THE  INHABITANTS  OF  OCEANIC  ISLANDS. 

We  now  come  to  the  last  of  the  three  classes  of  facts, 
which  I  have  selected  as  presenting  the  greatest  amount 
of  difficulty  with  respect  to  distribution,  on  the  view  that 
not  only  all  the  individuals  of  the  same  species  have 


410 


INHABITANTS  OF  OCEANIC  ISLANDS. 


migrated  from  some  one  area,  but  that  allied  species, 
although  now  inhabiting  the  most  distant  points,  have  pro¬ 
ceeded  from  a  single  area,  the  birthplace  of  their  early  pro¬ 
genitors.  I  have  already  given  my  reasons  for  disbeliev¬ 
ing  in  continental  extensions  within  the  period  of  existing 
species  on  so  enormous  a  scale  that  all  the  many  islands 
of  the  several  oceans  were  thus  stocked  with  their  present 
terrestrial  inhabitants.  This  view  removes  many  difficul¬ 
ties,  but  it  does  not  accord  with  all  the  facts  in  regard  to 
the  productions  of  islands.  In  the  following  remarks  I 
shall  not  confine  myself  to  the  mere  question  of  dispersal, 
but  shall  consider  some  other  cases  bearing  on  the  truth  of 
the  two  theories  of  independent  creation  and  of  descent 
with  modification. 

The  species  of  all  kinds  which  inhabit  oceanic  islands 
are  few  in  number  compared  with  those  on  equal  continen¬ 
tal  areas:  Alph.  de  Candolle  admits  this  for  plants,  and 
Wollaston  for  insects,  blew  Zealand,  for  instance,  with 
its  lofty  mountains  and  diversified  stations,  extending  over 
780  miles  of  latitude,  together  with  the  outlying  islands  of 
Auckland,  Campbell  and  Chatham,  contain  altogether 
only  960  kinds  of  flowering  plants;  if  we  compare  this  moder¬ 
ate  number  with  the  species  which  swarm  over  equal  areas 
in  Southwestern  Australia  or  at  the  Cape  of  Good  Hope, 
we  must  admit  that  some  cause,  independently  of  different 
physical  conditions,  has  given  rise  to  so  great  a  difference 
in  number.  Even  the  uniform  county  of  Cambridge  has 
847  plants,  and  the  little  island  of  Anglesea  764,  but  a 
few  ferns  and  a  few  introduced  plants  are  included  in 
these  numbers,  and  the  comparison  in  some  other  respects 
is  not  quite  fair.  We  have  evidence  that  the  barren  island 
of  Ascension  aboriginally  possessed  less  than  half  a  dozen 
flowering  plants;  yet  many  species  have  now  become 
naturalized  on  it,  as  they  have  in  New  Zealand  and  on 
every  other  oceanic  island  which  can  be  named.  In  St. 
Helena  there  is  reason  to  believe  that  the  naturalized  plants 
and  animals  have  nearly  or  quite  exterminated  many  native 
productions.  He  who  admits  the  doctrine  of  the  creation 
of  each  separate  species,  will  have  to  admit  that  a  sufficient 
number  of  the  best  adapted  plants  and  animals  were  not 
created  for  oceanic  islands;  for  man  has  unintentionally 
stocked  them  far  more  fully  and  perfectly  than  did  nature. 


INHABITANTS  OF  OCEANIC  ISLANDS. 


411 


Although  in  oceanic  islands  the  species  are  few  in 
number,  the  proportion  of  endemic  kinds  (i.  e.  those 
found  nowhere  else  in  the  world)  is  often  extremely  large. 
If  we  compare,  for  instance,  the  number  of  endemic  land- 
shells  in  Madeira,  or  of  endemic  birds  in  the  Galapagos 
Archipelago,  with  the  number  found  on  any  continent, 
and  then  compare  the  area  of  the  island  with  that  of  the 
continent,  we  shall  see  that  this  is  true.  This  fact  might 
have  been  theoretically  expected,  for,  as  already  explained, 
species  occasionally  arriving,  after  long  intervals  of  time  in 
the  new  and  isolated  district,  and  having  to  compete  with 
new  associates,  would  be  eminently  liable  to  modification, 
and  would  often  produce  groups  of  modified  descendants. 
But  it  by  no  means  follows  that,  because  in  an  islaud 
nearly  all  the  species  of  one  class  are  peculiar,  those  of 
another  class,  or  of  another  section  of  the  same  class,  are 
peculiar;  and  this  difference  seems  to  depend  partly  on  the 
species  which  are  not  modified  having  immigrated  in  a 
body,  so  that  their  mutual  relations  have  not  been  much 
disturbed;  and  partly  on  the  frequent  arrival  of  unmodified 
immigrants  from  the  mother-country,  with  which  the 
insular  forms  have  intercrossed.  It  should  be  borne  in 
mind  that  the  offspring  of  such  crosses  would  certainly 
gain  in  vigor;  so  that  even  an  occasional  cross  would  pro¬ 
duce  more  effect  than  might  have  been  anticipated.  I  will 
give  a  few  illustrations  of  the  foregoing  remarks:  in  the 
Galapagos  Islands  there  are  twenty-six  land  birds;  of  these, 
twenty-one  (or  perhaps  twenty-three)  are  peculiar,  whereas 
of  the  eleven  marine  birds  only  two  are  peculiar;  and  it  is 
obvious  that  marine  birds  could  arrive  at  these  islands 
much  more  easily  and  frequently  than  land  birds.  Ber¬ 
muda,  on  the  other  hand,  which  lies  at  about  the  same 
distance  from  North  America  as  the  Galapagos  Islands  do 
from  South  America,  and  which  has  a  very  peculiar  soil, 
does  not  possess  a  single  endemic  land  bird;  and  we  know 
from  Mr.  J.  M.  Jones’  admirable  account  of  Bermuda, 
that  very  many  North  American  birds  occasionally  or  even 
frequently  visit  this  island.  Almost  every  year,  as  I 
am  informed  by  Mr.  E.  V.  Harcourt,  many  European  and 
African  birds  are  blown  to  Madeira;  this  island  is  inhabited 
by  ninety-nine  kinds,  of  which  one  alone  is  peculiar,  though 
very  closely  related  to  a  European  form;  and  three  or  four 


412 


IN II A  BIT  A  NTS  OF  OCEANIC  ISLANDS. 


other  species  are  confined  to  this  island  and  to  the  Canaries. 
So  that  the  Islands  of  Bermuda  and  Madeira  have  been 
stocked  from  the  neighboring  continents  with  birds,  which 
for  long  ages  have  there  struggled  together,  and  have 
become  mutually  co-adapted.  Hence,  when  settled  in  their 
new  homes,  each  kind  will  have  been  kept  by  the  others  to 
its  proper  place  and  habits,  and  will  consequently  have 
been  but  little  liable  to  modification.  Any  tendency  to 
modification  will  also  have  been  checked  by  intercrossing 
with  the  unmodified  immigrants,  often  arriving  from  the 
mother-country.  Madeira  again  is  inhabited  by  a  wonder¬ 
ful  number  of  peculiar  land-shells,  whereas  not  one  species 
of  sea-shell  is  peculiar  to  its  shores:  now,  though  we  do 
not  know  how  sea-shells  are  dispersed,  yet  we  can  see  that 
their  eggs  or  larvae,  perhaps  attached  to  sea- weed  or  float¬ 
ing  timber,  or  to  the  feet  of  wading  birds,  might  be  trans¬ 
ported  across  three  or  four  hundred  miles  of  open  sea  far 
more  easily  than  land-shells.  The  different  orders  of 
insects  inhabiting  Madeira  present  nearly  parallel  cases. 

Oceanic  islands  are  sometimes  deficient  in  animals  of 
certain  whole  classes,  and  their  places  are  occupied  by 
other  classes;  thus  in  the  Galapagos  Islands  reptiles,  and 
in  New  Zealand  gigantic  wingless  birds,  take,  or  recently 
took,  the  place  of  mammals.  Although  New  Zealand  is  here 
spoken  of  as  an  oceanic  island,  it  is  in  some  degree  doubtful 
whether  it  should  be  so  ranked;  it  is  of  large  size,  and  is 
not  separated  from  Australia  by  a  profoundly .  deep  sea; 
from  its  geological  character  and  the  direction  of  its  mount¬ 
ain  ranges,  the  Rev.  W.  B.  Clarke  has  lately  maintained 
that  this  island,  as  well  as  New  Caledonia,  should  be  con¬ 
sidered  as  appurtenances  of  Australia.  Turning  to  plants, 
Dr.  Hooker  has  shown  that  in  the  Galapagos  Islands  the 
proportional  numbers  of  the  different  orders  are  very  dif¬ 
ferent  from  what  they  are  elsewhere.  All  such  differences 
in  number,  and  the  absence  of  certain  whole  groups  of 
animals  and  plants,  are  generally  accounted  for  by  sup¬ 
posed  differences  in  the  physical  conditions  of  the  islands; 
but  this  explanation  is  not  a  little  doubtful.  Facility  of 
immigration  seems  to  have  been  fully  as  important  as  the 
nature  of  the  conditions. 

Many  remarkable  little  facts  could  he  given  with  respect 
to  the  inhabitants  3f  oceanic  islands.  For  instance,,  in 


INHABITANTS  OF  OCEANIC  ISLANDS.  413 

certain  islands  not  tenanted  by  a  single  mammal,  some  of 
the  endemic  plants  have  beautifully  hooked  seeds;  yet  few 
relations  are  more  manifest  than  that  hooks  serve  for  the 
transportal  of  seeds  in  the  wool  or  fur  of  quadrupeds. 
But  a  hooked  seed  might  be  carried  to  an  island  by  other 
means;  and  the  plant  then  becoming  modified  would  form 
an  endemic  species,  still  retaining  its  hooks,  which  would 
form  a  useless  appendage,  like  the  shrivelled  wings  under 
the  soldered  wing-covers  of  many  insular  beetles.  Again, 
islands  often  possess  trees  or  bushes  belonging  to  orders 
which  elsewhere  include  only  herbaceous  species;  now 
trees,  as  Alph.  de  Candolle  has  shown,  generally  have, 
whatever  the  cause  may  be,  confined  ranges.  Hence  trees 
would  be  little  likely  to  reach  distant  oceanic  islands;  and 
an  herbaceous  plant,  which  had  no  chance  of  successfully 
competing  with  the  many  fully  developed  trees  growing  on 
a  continent,  might,  when  established  on  an  island,  gain  an 
advantage  over  other  herbaceous  plants  by  growing  taller 
and  taller  and  overtopping  them.  In  this  case,  natural 
selection  would  tend  to  add  to  the  stature  of  the  plant,  to 
whatever  order  it  belonged,  and  thus  first  convert  it  into  a 
bush  and  then  into  a  tree. 

ABSENCE  OF  BATRACHIANS  AND  TERRESTRIAL  Tn  A.MMALS 

ON  OCEANIC  ISLANDS. 

With  respect  to  the  absence  of  whole  orders  of  animals 
on  oceanic  islands,  Bory  St.  Vincent  long  ago  remarked 
that  Batrachians  (frogs,  toads,  newts)  are  never  found  on 
any  of  the  many  islands  with  which  the  great  oceans  are 
'  studded.  I  have  taken  pains  to  verify  this  assertion,  and 
have  found  it  true,  with  the  exception  of  New  Zealand, 
New  Caledonia,  the  Andaman  Islands,  and  perhaps  the 
Solomon  Islands  and  the  Seychelles.  But  I  have  already 
remarked  that  it  is  doubtful  whether  New  Zealand  and 
New  Caledonia  ought  to  be  classed  as  oceanic  islands;  and 
this  is  still  more  doubtful  with  respect  to  the  Andaman  and 
Solomon  groups  and  the  Seychelles.  This  general  absence 
of  frogs,  toads  and  newts  on  so  many  true  oceanic  islands 
can  not  be  accounted  for  by  their  physical  conditions:  in¬ 
deed  it  seems  that  islands  are  peculiarly  fitted  for  these 
animals;  for  frogs  have  been  introduced  into  Madeira,  the 


414 


ABSENCE  CF  TERRESTRIAL 


Azores  and  Mauritius,  and  have  multiplied  so  as  to  become 
a  nuisance.  But  as  these  animals  and  their  spawn  are  im¬ 
mediately  killed  (with  the  exception,  as  far  as  known,  of 
one  Indian  species)  by  sea-water,  there  would  be  great 
difficulty  in  their  transportal  across  the  sea,  and  therefore 
we  can  see  why  they  do  not  exist  on  strictly  oceanic 
islands.  But  why,  on  the  theory  of  creation,  they  should 
not  have  been  created  there,  it  would  be  very  difficult  to 
explain. 

Mammals  offer  another  and  similar  case.  I  have  care¬ 
fully  searched  the  oldest  voyages,  and  have  not  found  a 
single  instance,  free  from  doubt,  of  a  terrestrial  mammal 
(excluding  domesticated  animals  kept  by  the  natives)  in¬ 
habiting  an  island  situated  about  300  miles  from  a  conti¬ 
nent  or  great  continental  island;  and  many  islands  situated 
at  a  much  less  distance  are  equally  barren.  The  Falkland 
Islands,  which  are  inhabited  by  a  wolf-like  fox,  come  near¬ 
est  to  an  exception;  but  this  group  cannot  be  considered 
as  oceanic,  as  it  lies  on  a  bank  in  connection  with  the 
mainland  at  a  distance  of  about  280  miles;  moreover,  ice¬ 
bergs  formerly  brought  bowlders  to  its  western  shores,  and 
they  may  have  formerly  transported  foxes,  as  now  fre¬ 
quently  happens  in  the  arctic  regions.  Yet  it  cannot  be 
said  that  small  islands  will  not  support  at  least  small  mam¬ 
mals,  for  they  occur  in  many  parts  of  the  world  on  very 
small  islands,  when  lying  close  to  a  continent;  and  hardly 
an  island  can  be  named  on  which  our  smaller  quadrupeds 
have  not  become  naturalized  and  greatly  multiplied.  It 
cannot  be  said,  on  the  ordinary  view  of  creation,  that  there 
has  not  been  time  for  the  creation  of  mammals;  many  vol¬ 
canic  islands  are  sufficiently  ancient,  as  shown  by  the 
stupendous  degradation  which  they  have  suffered,  and  by 
their  tertiary  strata:  there  has  also  been  time  for  the  pro¬ 
duction  of  endemic  species  belonging  to  other  classes;  and 
on  continents  it  is  known  that  new  species  of  mammals  ap¬ 
pear  and  disappear  at  a  quicker  rate  than  other  and  lower 
animals..  Although  terrestrial  mammals  do  not  occur  on 
oceanic  islands,  aerial  mammals  do  occur  on  almost  every 
island.  New  Zealand  possesses  two  bats  found  nowhere 
else  in  the  world:  Norfolk  Island,  the  Viti  Archipelago, 
the  Bonin  Islands,  the  Caroline  and  Marianne  Archi¬ 
pelagoes,  and  Mauritius,  all  possess  their  peculiar  bats. 


MAMMALS  ON  OCEANIC  ISLANDS. 


415 


Why,  it  may  be  asked,  has  the  supposed  creative  force 
produced  bats  and  no  other  mammals  on  remote  islands? 
On  my  view  this  question  can  easily  be  answered;  for  no 
terrestrial  mammal  can  be  transported  across  a  wide  space 
of  sea,  but  bats  can  fly  across.  Bats  have  been  seen  wan¬ 
dering  by  day  far  over  the  Atlantic  Ocean;  and  two  North 
American  species,  either  regularly  or  occasionally,  visit  Ber¬ 
muda,  at  the  distance  of  600  miles  from  the  mainland.  I 
hear  from  Mr.  Tomes,  who  has  specially  studied  this 
family,  that  many  species  have  enormous  ranges,  and  are 
found  on  continents  and  on  far  distant  islands.  Hence,  we 
have  only  to  suppose  that  such  wandering  species  have 
been  modified  in  their  new  homes  in  relation  to  their  new 
position,  and  we  can  understand  the  presence  of  endemic 
bats  on  oceanic  islands,  with  the  absence  of  all  other  ter¬ 
restrial  mammals. 

Another  interesting  relation  exists,  namely,  between 
the  depth  of  the  sea  separating  islands  from  each  other, 
or  from  the  nearest  continent,  and  the  degree  of  affinity 
of  their  mammalian  inhabitants.  Mr.  Windsor  Earl  has 
made  some  striking  observations  on  this  head,  since  greatly 
extended  by  Mr.  Wallace's  admirable  researches,  in  regard 
to  the  great  Malay  Archipelago,  which  is  traversed  near 
Celebes  by  a  space  of  deep  ocean,  and  this  separates  two 
widely  distinct  mammalian  faunas.  On  either  side,  the 
islands  stand  on  a  moderately  shallow  submarine  bank, 
and  these  islands  are  inhabited  by  the  same  or  by  closely 
allied  quadrupeds.  I  have  not  as  yet  had  time  to  follow 
up  this  subject  in  all  quarters  of  the  world;  but  as  far  as  I 
have  gone,  the  relation  holds  good.  For  instance,  Britain 
is  separated  by  a  shallow  channel  from  Europe,  and  the 
mammals  are  the  same  on  both  sides;  and  so  it  is  with  all 
the  islands  near  the  shores  of  Australia.  The  West  Indian 
Islands,  on  the  other  hand,  stand  on  a  deeply  submerged 
bank,  nearly  one  thousand  fathoms  in  depth,  and  here  we 
find  American  forms,  but  the  species  and  even  the  genera 
are  quite  distinct.  As  the  amount  of  modification  which 
animals  of  all  kinds  undergo  partly  depends  on  the  lapse 
of  time,  and  as  the  islands  which  are  separated  from  each 
other,  or  from  the  mainland,  by  shallow  channels,  are  more 
likely  to  have  been  continuously  united  within  a  recent 
period  than  the  islands  separated  by  deeper  channels,  we 


416 


ABSENCE  OF  TERRESTRIAL 


can  understand  how  it  is  that  a  relation  exists  between  the 
depth  of  the  sea  separating  two  mammalian  faunas,  and 
the  degree  of  their  affinity,  a  relation  which  is  quite  inex¬ 
plicable  on  the  theory  of  independent  acts  of  creation. 

The  foregoing  statements  in  regard  to  the  inhabitants  of 
oceanic  islands,  namely,  the  fewness  of  the  species,  with  a 
large  proportion  consisting  of  endemic  forms — the  mem¬ 
bers  of  certain  groups,  but  not  those  of  other  groups  in  the 
same  class,  having  been  modified — the  absence  of  certain 
Afhole  orders,  as  of  batrachians  and  of  terrestrial  mammals, 
notwithstanding  the  presence  of  aerial  bats,  the  singular 
proportions  of  certain  orders  of  plants,  herbaceous  forms 
having  been  developed  into  trees,  etc.,  seem  to  me  to  accord 
better  with  the  belief  in  the  efficiency  of  occasional  means 
of  transport,  carried  on  during  a  long  course  of  time,  than 
with  the  belief  in  the  former  connection  of  all  oceanic 
islands  with  the  nearest  continent;  for  on  this  latter  view 
it  is  probable  that  the  various  classes  would  have  immi¬ 
grated  more  uniformly,  and  from  the  species  having 
entered  in  a  body,  their  mutual  relations  would  not  have 
been  much  disturbed,  and  consequently,  they  would  either 
have  not  been  modified,  or  all  the  species  in  a  more  equa¬ 
ble  manner. 

I  do  not  deny  that  there  are  many  and  serious  difficul¬ 
ties  in  understanding  how  many  of  the  inhabitants  of  the 
more  remote  islands,  whether  still  retaining  the  same  spe¬ 
cific  form  or  subsequently  modified,  have  reached  their 
present  homes.  But  the  probability  of  other  islands  having 
once  existed  as  halting-places,  of  which  not  a  wreck  now 
remains,  must  not  be  overlooked.  I  will  specify  one  diffi¬ 
cult  case.  Almost  all  oceanic  islands,  even  the  most 
isolated  and  smallest,  are  inhabited  by  land-shells,  gener¬ 
ally  by  endemic  species,  but  sometimes  by  species  found 
elsewhere,  striking  instances  of  which  have  been  given 
by  Dr.  A.  A.  Gould  in  relation  to  the  Pacific.  Now  it 
is  notorious  that  land-shells  are  easily  killed  by  sea¬ 
water;  their  eggs,  at  least  such  as  I  have  tried,  sink  in 
it  and  are  killed.  Yet  there  must  be  some  unknown, 
but  occasionally  efficient  means  for  their  transportal. 
Would  the  just-hatched  young  sometimes  adhere  to  the 
feet  of  birds  roosting  on  the  ground  and  thus  get  trans¬ 
ported?  It  occurred  to  me  that  land-shells,  when  hyber- 


MAMMALS  ON  OCEANIC  ISLANDS. 


41? 


Bating  and  having  a  membranous  diaphragm  over  the 
mouth  of  the  shell,  might  be  floated  in  chinks  of  drifted 
timber  across  moderately  wide  arms  of  the  sea.  And  I  find 
that  several  species  in  this  state  withstand  uninjured  an  im¬ 
mersion  in  sea-water  during  seven  days.  One  shell,  the  Helix 
pomatia,  after  having  been  thus  treated,  and  again  hyber- 
nating,  was  put  into  sea-water  for  twenty  days  and  perfectly 
recovered.  During  this  length  of  time  the  shell  might 
have  been  carried  by  a  marine  current  of  average  swiftness 
to  a  distance  of  660  geographical  miles.  As  this  Helix  has 
a  thick  calcareous  operculum  I  removed  it,  and  when  it 
had  formed  a  new  membranous  one,  I  again  immersed  it 
for  fourteen  days  in  sea-water,  and  again  it  recovered  and 
crawled  away.  Baron  Aucapitaine  has  since  tried  similar 
experiments.  He  placed  100  land-shells,  belonging  to  ten 
species,  in  a  box  pierced  with  holes,  and  immersed  it  for  a 
fortnight  in  the  sea.  Out  of  the  hundred  shells  twenty- 
seven  recovered.  The  presence  of  an  operculum  seems  to 
have  been  of  importance,  as  out  of  twelve  specimens  of 
Cyclostoma  elegans,  which  is  thus  furnished,  eleven  re¬ 
vived.  It  is  remarkable,  seeing  how  well  the  Helix  pomatia 
resisted  with  me  the  salt-water,  that  not  one  of  fifty-four 
specimens  belonging  to  four  other  species  of  Helix  tried  by 
Aucapitaine  recovered.  It  is,  however,  not  at  all  probable 
that  land-shells  have  often  been  thus  transported;  the 
feet  of  birds  offer  a  more  probable  method. 

ON  THE  RELATIONS  OF  THE  INHABITANTS  OF  ISLANDS  TO 
THOSE  OF  THE  NEAREST  MAINLAND. 

The  most  striking  and  important  fact  for  us  is  the 
affinity  of  the  species  which  inhabit  islands  to  those  of  the 
nearest  mainland,  without  being  actually  the  same. 
Numerous  instances  could  be  given.  The  Galapagos  Arch¬ 
ipelago,  situated  under  the  equator,  lies  at  the  distance  of 
between  500  and  600  miles  from  the  shores  of  South 
America.  Here  almost  every  product  of  the  land  and 
of  the  water  bears  the  unmistakable  stamp  of  the  Amer¬ 
ican  continent.  There  are  twenty-six  land  birds.  Of 
these  twenty-one,  or  perhaps  twenty-three,  are  ranked  as 
distinct  species,  and  would  commonly  be  assumed  to  have 
been  here  created;  yet  the  close  affinity  of  most  of  these 


i 


418 


RELATIONS  OF  THE  INHABITANTS  OF 


birds  to  American  species  is  manifest  in  every  character  in 
their  habits,  gestures  and  tones  of  voice.  So  it  is  with  the 
other  animals,  and  with  a  large  proportion  of  the  plants, 
as  shown  by  Dr.  Hooker  in  his  admirable  Flora  of  this 
archipelago.  The  naturalist,  looking  at  the  inhabitants  of 
these  volcanic  islands  in  the  Pacific,  distant  several  hun¬ 
dred  miles  from  the  continent,  feels  that  he  is  standing  on 
American  land.  Why  should  this  be  so?  Why  should  the 
species  which  are  supposed  to  have  been  created  in  the 
Galapagos  Archipelago,  and  nowhere  else,  bear  so  plainly 
the  stamp  of  affinity  to  those  created  in  America? 
There  is  nothing  in  the  conditions  of  life,  in  the 
geological  nature  of  the  islands,  in  their  height  or 
climate,  or  in  the  proportions  in  which  the  several  classes 
aie  associated  together,  which  closely  resembles  the 
conditions  of  the  South  American  coast.  In  fact, 
there  is  a  considerable  dissimilarity  in  all  these  respects. 
On  the  other  hand,  there  is  a  considerable  degree  of  resem¬ 
blance  in  the  volcanic  nature  of  the  soil,  in  the  climate, 
height,  and  size  of  the  islands,  between  the  Galapagos  and 
Cape  Verde  Archipelagos:  but  what  an  entire  and  abso¬ 
lute  difference  in  their  inhabitants!  The  inhabitants  of 
the  Cape  Verde  Islands  are  related  to  those  of  Africa,  like 
those  of  the  Galapagos  to  America.  Facts,  such  as  these, 
admit  of  no  sort  of  explanation  on  the  ordinary  view  of  in¬ 
dependent  creation;  whereas,  on  the  view  here  maintained, 
it  is  obvious  that  the  Galapagos  Islands  would  be  likely  to 
receive  colonists  from  America,  whether  by  occasional 
means  of  transport  or  (though  I  do  not  believe  in  this  doc¬ 
trine)  by  formerly  continuous  land,  and  the  Cape  Verde 
Islands  from  Africa;  such  colonists  would  be  liable  to 
modification — the  principle  of  inheritance  still  betraying 
their  original  birthplace. 

Many  analogous  facts  could  be  given:  indeed  it  is  an 
almost  universal  rule  that  the  endemic  productions  of 
islands  are  related  to  those  of  the  nearest  continent,  or  of 
the  nearest  large  island.  The  exceptions  are  few,  and 
most  of  them  can  be  explained.  Thus,  although  Kergue¬ 
len  Land  stands  nearer  to  Africa  than  to  America,  the 
plants  are  related,  and  that  very  closely,  as  we  know  from 
Dr.  Hooker’s  account,  to  those  of  America:  but  on  the 
view  that  this  island  has  been  mainly  stocked  by  seeds 


ISLANDS  TO  THOSE  OF  THE  MAINLAND.  419 


brought  with  earth  and  stones  on  icebergs,  drifted  by  the 
prevailing  currents,  this  anomaly  disappears.  New  Zealand 
in  its  endemic  planes  is  much  more  closely  related  to  Aus¬ 
tralia,  the  nearest  mainland,  than  to  any  other  region:  and 
this  is  what  might  have  been  expected;  but  it  is  also 
plainly  related  to  South  America,  which,  although  the 
next  nearest  continent,  is  so  enormously  remote,  that  the 
fact  becomes  an  anomaly.  But  this  difficulty  partially  dis¬ 
appears  on  the  view  that  New  Zealand,  South  America, 
and  the  other  southern  lands,  have  been  stocked  in  part 
from  a  nearly  intermediate  though  distant  point,  namely, 
from  the  antarctic  islands,  when  they  were  clothed  with 
vegetation,  during  a  warmer  tertiary  period,  before  the 
commencement  of  the  last  Glacial  period.  The  affinity, 
which,  though  feeble,  I  am  assured  by  Dr.  Hooker  is  real, 
between  the  flora  of  the  south-western  corner  of  Australia 
and  of  the  Cape  of  Good  Hope,  is  a  far  more  remarkable 
case;  but  this  affinity  is  confined  to  the  plants,  and  will, 
no  doubt,  some  day  be  explained. 

The  same  law  which  has  determined  the  relationship  be¬ 
tween  the  inhabitants  of  islands  and  the  nearest  mainland, 
is  sometimes  displayed  on  a  small  scale,  but  in  a  most  in¬ 
teresting  manner,  within  the  limits  of  the  same  archi¬ 
pelago.  Thus  each  separate  island  of  the  Galapagos 
Archipelago  is  tenanted,  and  the  fact  is  a  marvelous 
one,  by  many  distinct  species;  but  these  species  are 
related  to  each  other  in  a  very  much  closer  manner 
than  to  the  inhabitants  of  the  American  continent,  or  of 
any  other  quarter  of  the  world.  This  is  what  might 
have  been  expected,  for  islands  situated  so  near  to  each 
other  would  almost  necessarily  receive  immigrants  from  the 
some  original  source,  and  from  each  other.  But  how  is  it 
that  many  of  the  immigrants  have  been  differently  modi¬ 
fied,  though  only  in  a  small  degree,  in  islands  situated 
within  sight  of  each  other,  having  the  same  geolog¬ 
ical  nature,  the  same  height,  climate,  etc.  ?  This  long 
appeared  to  me  a  great  difficulty:  but  it  arises  in  chief 
part  from  the  deeply-seated  error  of  considering  the  phys¬ 
ical  conditions  of  a  country  as  the  most  important; 
whereas  it  cannot  be  disputed  that  the  nature  of  the 
other  species  with  which  each  has  to  compete,  is  at 
least  as  important,  and  generally  a  far  more  import- 


420 


RELATIONS  OF  THE  INHABITANTS  01 


ant  element  of  success.  Now,  if  we  look  to  the  species 
which  inhabit  the  Galapagos  Archipelago,  and  are  likewise 
found  in  other  parts  of  the  world,  we  find  that  they  differ 
considerably  in  the  several  islands.  This  difference  might 
indeed  have  been  expected  if  the  islands  have  been  stocked 
by  occasional  means  of  transport — a  seed,  for  instance,  of 
one  plant  having  been  brought  to  one  island,  and  that  of 
another  plant  to  another  island,  though  all  proceeding 
from  the  same  general  source.  Hence,  when  in  former 
times  an  immigrant  first  settled  on  one  of  the  islands,  or 
when  it  subsequently  spread  from  one  to  another,  it  would 
undoubtedly  be  exposed  to  different  conditions  in  the  dif¬ 
ferent  islands,  for  it  would  have  to  compete  with  a  differ¬ 
ent  set  of  organisms;  a  plant,  for  instance,  would  find  the 
ground  best  fitted  for  it  occupied  by  somewhat  different 
species  in  the  different  islands,  and  would  be  exposed  to 
the  attacks  of  somewhat  different  enemies.  If,  then,  it 
varied,  natural  selection  would  probably  favor  different 
varieties  in  the  different  islands.  Some  species,  however, 
might  spread  and  yet  retain  the  same  character  throughout 
the"  group,  just  as  we  see  some  species  spreading  widely 
throughout  a  continent  and  remaining  the  same. 

The  really  surprising  fact  in  this  case  of  the  Galapagos 
Archipelago,  and  in  a  lesser  degree  in  some  analogous 
cases,  is  that  each  new  species  after  being  formed  in  any 
one  island,  did  not  spread  quickly  to  the  other  islands. 
But  the  islands,  though  in  sight  of  each  other,  are  sepa¬ 
rated  by  deep  arms  of  the  sea,  in  most  cases  wider  than  the 
British  Channel,  and  there  is  no  reason  to  suppose  that 
they  have  at  any  former  period  been  continuously  united. 
The  currents  of  the  sea  are  rapid  and  deep  between  the 
islands,  and  gales  of  wind  are  extraordinarily  rare;  so  that 
the  islands  are  far  more  effectually  separated  from  each  other 
than  they  appear  on  a  map.  Nevertheless,  some  of  the 
species,  both  of  those  found  in  other  parts  of  the  world 
and  of  those  confined  to  the  archipelago,  are  common  to 
the  several  islands;  and  we  may  infer  from  the  present 
manner  of  distribution  that  they  have  spread  from  one 
island  to  the  others.  But  we  often  take,  I  think,  an 
erroneous  view  of  the  probability  of  closely  allied  species 
invading  each  other's  territory,  when  put  into  free  inter¬ 
communication,  Undoubtedly,  if  one  species  has  any 


islands  to  Those  of  the  mainland.  421 

advantage  over  another,  it  will  in  a  very  brief  time 
wholly  or  in  part  supplant  it;  but  if  both  are  equally  well 
fitted  for  their  own  places,  both  will  probably  hold  their 
separate  places  for  almost  any  length  of  time.  Being 
familiar  with  the  fact  that  many  species,  naturalized 
through  man's  agency,  have  spread  with  astonishing 
rapidity  over  wide  areas,  we  are  apt  to  infer  that  most 
species  would  thus  spread;  but  we  should  remember  that 
the  species  which  become  naturalized  in  new  countries 
are  not  generally  closely  allied  to  the  aboriginal  inhabi¬ 
tants,  but  are  very  distinct  forms,  belonging  in  a  large 
proportion  of  cases,  as  shown  by  Alph.  de  Candolle, 
to  distinct  genera.  In  the  Galapagos  Archipelago,  many 
even  of  the  birds,  though  so  well  adapted  for  flying 
from  island  to  island,  differ  on  the  different  islands; 
thus  there  are  three  closely  allied  species  of  mocking- 
thrush,  each  confined  to  its  own  island.  Now  let  us 
suppose  the  mocking-thrush  of  Chatham  Island  to  be 
blown  to  Charles  Island,  which  has  its  own  mocking- 
thrush;  why  should  it  succeed  in  establishing  itself  there? 
We  may  safely  infer  that  Charles  Island  is  well  stocked  with 
its  own  species,  for  annually  more  eggs  are  laid  and  young 
birds  hatched  than  can  possibly  be  reared;  and  we  may 
infer  that  the  mocking-thrush  peculiar  to  Charles  Island  is 
at  least  as  well  fitted  for  its  home  as  is  the  species  peculiar 
to  Chatham  Island.  Sir  C.  Lyell  and  Mr.  Wollaston 
have  communicated  to  me  a  remarkable  fact  bearing  on 
this  subject;  namely,  that  Madeira  and  the  adjoining  islet 
of  Porto  Santo  possesses  many  distinct  but  representative 
species  of  land-shells,  some  of  which  live  in  crevices  of 
stone;  and  although  large  quantities  of  stone  are  annually 
transported  from  Porto  Santo  to  Madeira,  yet  this  latter 
island  has  not  become  colonized  by  the  Porto  Santo 
species;  nevertheless,  both  islands  have  been  colonized  by 
European  land-shells,  which  no  doubt  had  some  advantage 
over  the  indigenous  species.  From  these  considerations  I 
think  we  need  not  greatly  marvel  at  the  endemic  species 
which  inhabit  the  several  islands  of  the  Galapagos  Archi¬ 
pelago  not  having  all  spread  from  island  to  island.  On 
the  same  continent,  also,  preoccupation  has  probably 
played  an  important  part  in  checking  the  commingling  of 
the  species  which  inhabit  different  districts  with  nearly  the 


422  RELATIONS  OF  THE  INHABITANTS  OF 

same  physical  conditions.  Thus,  the  south-east  and  south¬ 
west  corners  of  Australia  have  nearly  the  same  physical 
conditions,  and  are  united  by  continuous  land,  yet  they  are 
inhabited  by  a  vast  number  of  distinct  mammals,  birds 
and  plants;  so  it  is,  according  to  Mr.  Bates,  with  the 
butterflies  and  other  animals  inhabiting  the  great,  open, 
and  continuous  valley  of  the  Amazons. 

The  same  principle  which  governs  the  general  character 
of  the  inhabitants  of  oceanic  islands,  namely,  the  relation 
to  the  source  whence  colonists  could  have  been  most 
easily  derived,  together  with  their  subsequent  modifica¬ 
tion,  is  of  the  widest  application  throughout  nature.  We 
see  this  on  every  mountain-summit,  in  every  lake  and 
marsh.  For  Alpine  species,  excepting  in  as  far  as  the 
same  species  have  become  widely  spread  during  the  Glacial 
epoch,  are  related  to  those  of  the  surrounding  lowlands; 
thus  we  have  in  South  America,  Alpine  humming-birds, 
Alpine  rodents,  Alpine  plants,  etc.,  all  strictly  belonging 
to  American  forms;  and  it  is  obvious  that  a  mountain,  as 
it  became  slowly  upheaved,  would  be  colonized  from  the 
surrounding  lowlands.  So  it.  is  with  the  inhabitants  of 
lakes  and  marshes,  excepting  in  so  far  as  great  facility  of 
transport  has  allowed  the  same  forms  to  prevail  through¬ 
out  large  portions  of  the  world.  We  see  the  same  princi¬ 
ple  in  the  character  of  most  of  the  blind  animals  inhabiting 
the  caves  of  America  and  of  Europe.  Other  analogous 
facts  could  be  given.  It  will,  I  believe,  be  found  uni¬ 
versally  true,  that  wherever  in  two  regions,  let  them  be 
ever,  so  distant,  many  closely  allied  or  representative' 
species  occur,  there  will  likewise  be  found  some  identical 
species;  and  wherever  many  closely-allied  species  occur, 
there  will  be  found .  many  forms  which  some  naturalists 
rank  as  distinct  species,  and  others  as  mere  varieties;  these 
doubtful  forms  showing  us  the  steps  in  the  progress  of 
modification. 

.  The  relation  between  the  power  and  extent  of  migra¬ 
tion  in  certain  species,  either  at  the  present  or 
at .  some  former  period,  and  the  existence  at  remote 
points  of  the  world  of  closely  allied  species,  is  shown 
in  another  and  more  general  way.  Mr.  Gould  remarked 
to  me  long  ago,  that  in  those  genera  of  birds  which  range 
over  the  world,  many  of  the  species  have  very  wide  ranges. 


ISLANDS  TO  THOSE  OF  THE  MAINLAND .  423 

I  can  hardly  doubt  that  this  rule  is  generally  true,  though 
difficult  of  proof.  Among  mammals,  we  see  it  strikingly 
displayed  in  bats,  and  in  a  lesser  degree  in  the  Felidae  and 
Canidae.  We  see  the  same  rule  in  the  distribution  of  butter¬ 
flies  and  beetles.  So  it  is  with  most  of  the  inhabitants  of 
fresh  water,  for  many  of  the  genera  in  the  most  distinct 
classes  range  over  the  world,  and  many  of  the  species  have 
enormous  ranges.  It  is  not  meant  that  all,  but  that  some 
of  the  species  have  very  wide  ranges  in  the  genera  which 
range  very  widely.  Nor  is  it  meant  that  the  species  in 
such  genera  have,  on  an  average,  a  very  wide  range;  for 
this  will  largely  depend  on  how  far  the  process  of  modifica¬ 
tion  has  gone;  for  instance,  two  varieties  of  the  same 
species  inhabit  America  and  Europe,  and  thus  the  species 
has  an  immense  range;  but,  if  variation  were  to  be  carried 
a  little  further,  the  two  varieties  would  be  ranked  as  dis¬ 
tinct  species,  and  their  range  would  be  greatly  reduced. 
Still  less  is  it  meant,  that  species  which  have  the  capacity 
of  crossing  barriers  and  ranging  widely,  as  in  the  case  of 
certain  powerfully- winged  birds,  will  necessarily  range 
widely;  for  we  should  never  forget  that  to  range  widely 
implies  not  only  the  power  of  crossing  barriers,  but  the 
more  important  power  of  being  victorious  in  distant  lands 
in  the  struggle  for  life  with  foreign  associates.  But  accord¬ 
ing  to  the  view  that  all  the  species  of  a  genus,  though  dis¬ 
tributed  to  the  most  remote  points  of  the  world,  are 
descended  from  a  single  progenitor,  we  ought  to  find,  and 
I  believe  as  a  general  rule  we  do  find,  that  some  at  least  of 
the  species  range  very  widely. 

We  should  bear  in  mind  that  many  genera  in  all  classes 
are  of  ancient  origin,  and  the  species  in  this  case  will 
have  had  ample  time  for  dispersal  and  subsequent  modifi¬ 
cation.  There  is  also  reason  to  believe,  from  geological 
evidence,  that  within  each  great  class  the  lower  organisms 
change  at  a  slower  rate  than  the  higher;  consequently  they 
will  have  had  a  better  chance  of  ranging  widely  and  of  still 
retaining  the  same  specific  character.  This  fact,  together 
with  that  of  the  seeds  and  eggs  of  most  lowly  organized 
forms  being  very  minute  and  better  fitted  for  distant  trans- 
portal,  probably  accounts  for  a  law  which  has  long  been 
observed,  and  which  has  lately  been  discussed  by  Alph.  de 
Candolle  in  regard  to  plants,  namely,  that  the  lower  any 
group  of  organisms  stands  the  more  widely  it  ranges. 


424 


SUMMARY. 


The  relations  just  discussed — namely,  lower  organisms 
ranging  more  widely  than  the  higher — some  of  the  species 
of  widely- ranging  genera  themselves  ranging  widely  — 
such  facts,  as  alpine,  lacustrine,  and  marsh  productions 
being  generally  related  to  those  which  live  on  the  surround¬ 
ing  low  lands  and  dry  lands — the  striking  relationship 
between  the  inhabitants  of  islands  and  those  of  the  nearest 
mainland — the  still  closer  relationship  of  the  distinct  in¬ 
habitants  of  the  islands  in  the  same  archipelago — are  inex¬ 
plicable  on  the  ordinary  view  of  the  independent  creation 
of  each  species,  but  are  explicable  if  we  admit  colonization 
from  the  nearest  or  readiest  source,  together  with  the  sub¬ 
sequent  adaptation  of  the  colonists  to  their  new  homes. 

SUMMARY  OF  THE  LAST  AND  PRESENT  CHAPTERS. 

In  these  chapters  I  have  endeavored  to  show  that  if  we 
make  due  allowance  for  our  ignorance  of  the  full  effects  of 
changes  of  climate  and  of  the  level  of  the  land,  which 
have  certainly  occurred  within  the  recent  period,  and  of 
other  changes  which  have  probably  occurred — if  we  re¬ 
member  how  ignorant  we  are  with  respect  to  the  many 
curious  means  of  occasional  transport — if  we  bear  in  mind, 
and  this  is  a  very  important  consideration,  how  often  a 
species  may  have  ranged  continuously  over  a  wide  area, 
and  then  have  become  extinct  in  the  intermediate  tracts — 
the  difficulty  is  not  insuperable  in  believing  that  all  the 
individuals  of  the  same  species,  wherever  found,  are 
descended  from  common  parents.  And  we  are  led  to  this 
conclusion,  which  has  been  arrived  at  by  many  naturalists 
under  the  designation  of  single  centers  of  creation,  by 
various  general  considerations,  more  especially  from  the 
importance  of  barriers  of  all  kinds,  and  from  the  ana¬ 
logical  distribution  of  subgenera,  genera  and  families. 

With  respect  to  distinct  species  belonging  to  the  same 
genus,  which  on  our  theory  have  spread  from  one  parent- 
source;  if  we  make  the  same  allowances  as  before  for  our 
ignorance,  and  remember  that  some  forms  of  life  have 
changed  very  slowly,  enormous  periods  of  time  having  been 
thus  granted  for  their  migration,  the  difficulties  are  far 
from  insuperable;  though  in  this  case,  as  in  that  of  the 
individuals  of  the  same  species,  they  are  often  great. 


SUMMARY. 


425 

I  .£s  exemplifying  the  effects  of  climatical  changes  on  dis¬ 
tribution,  I  have  attempted  to  show  how  important  a  part 
the  last  Glacial  period  has  played,  which  affected  even  the 
equatorial  regions,  and  which,  during  the  alternations  of; 
the  cold  in  the  north  and  the  south,  allowed  the  produc¬ 
tions  of  opposite  hemispheres  to  mingle,  and  left  some  of 
them  stranded  on  the  mountain-summits  in  all  parts  of  the 
world.  As  showing  how  diversified  are  the  means  of  oc¬ 
casional  transport,  I  have  discussed  at  some  little  length 
the  means  of  dispersal  of  fresh- water  productions. 

.  tlie  difficulties  be  not  insuperable  in  admitting  that 
m  the  long  course  of  time  all  the  individuals  of  the 
same  species,  and  likewise  of  the  several  species  belonging 

<  to  the  same  genus,  have  proceeded  from  some  one  source*; 
then  all  the  grand  leading  facts  of  geographical  distribution 
are  explicable  on  the  theory  of  migration,  together  with 
subsequent  modification  and  the  multiplication  of  new 
forms.  We  can  thus  understand  the  high  importance  of 
barriers,  whether  of  land  or  water,  in  not  only  separating 
but  in  apparently  forming  the  several  zoological  and 
botanical  provinces.  We  can  thus  understand  the  con¬ 
centration  of  related  species  within  the  same  areas;  and 
how  it  is  that  under  different  latitudes,  for  instance,  in 
South  Ameiica,  the  inhabitants  of  the  plains  and  mount¬ 
ains,  of  the  forests,  marshes  and  deserts,  are  linked 
together  in  so  mysterious  a  manner,  and  are  likewise 
linked  to  the  extinct  beings  which  formerly  inhabited 
the  same  continent.  Bearing  in  mind  that  the  mutual 
relation  of  organism  to  organism  is  of  the  highest  im¬ 
portance,  we  can  see  why  two  areas,  having  nearly  the 
same  physical  conditions,  should  often  be  inhabited  by 
very  different  forms  of  life;  for  according  to  the  length 
of  time  which  has  elapsed  since  the  colonists  entered  one 
of  the  regions,  or  both;  according  to  the  nature  of  the 
communication  which  allowed  certain  forms  and  not  others 
to  enter,  either  in  greater  or  lesser  numbers;  according  or 
not  as  those  which  entered  happened  to  come  into  more 
or  less  direct  competition  with  each  other  and  with  the 
aborigines;  and  according  as  the  immigrants  were  capable 
of  varying  more  or  less  rapidlv,  there  would  ensue  in  the 
two  or  more  regions,  independently  of  their  physical  con¬ 
ditions,  infinitely  diversified  conditions  of  life;  there  would 


426 


SUMMARY. 


\ 


be  an  almost  endless  amount  of  organic  action  and  reaction, 
and  we  should  find  some  groups  of  beings  greatly,  and 
some  only  slightly  modified;  some  developed  in  great  force, 
some  existing  in  scanty  numbers — and  this  we  do  find  in 
the  several  great  geographical  provinces  of  the  world. 

On  these  same  principles  we  can  understand,  as  I  have 
endeavored  to  show,  why  oceanic  islands  should  have  few 
inhabitants,  but  that  of  these,  a  large  proportion  should  be 
endemic  or  peculiar;  and  why,  in  relation  to  the  means  of 
migration,  one  group  of  beings  should  have  all  its  species 
peculiar,  and  another  group,  even  within  the  same  class, 
should  have  all  its  species  the  same  with  those  in  an 
adjoining  quarter  of  the  world.  We  can  see  why  whole 
groups  of  organisms,  as  batrachians  and  terrestrial  mam¬ 
mals,  should  be  absent  from  oceanic  islands,  while  the 
most  isolated  islands  should  possess  their  own  peculiar 
species  of  aerial  mammals  or  bats.  We  can  see  why,  in 
islands,  there  should  be  some  relation  between  the  presence 
of  mammals,  in  a  more  or  less  modified  condition,  and  the 
depth  of  the  sea  between  such  islands  and  the  mainland. 
We  can  clearly  see  why  all  the  inhabitants  of  an  archipelago, 
though  specifically  distinct  on  the  several  islets,  should  be 
closely  related  to  each  other;  and  should  likewise  be 
related,  but  less  closely,  to  those  of  the  nearest  continent, 
or  other  source  whence  immigrants  might  have  been 
derived.  We  can  see  why,  if  there  exist  very  closely  allied 
or  representative  species  in  two  areas,  however  distant  from 
each  other,  some  identical  species  will  almost  always  there 
be  found. 

As  the  late  Edward  Forbes  often  insisted,  there  is  a 
striking  parallelism  in  the  laws  of  life  throughout  time 
and  space;  the  laws  governing  the  succession  of  forms  in 
past  times  being  nearly  the  same  with  those  governing  at 
the  present  time  the  differences  in  different  areas.  We 
see  this  in  many  facts.  The  endurance  of  each  species 
and  group  of  species  is  continuous  in  time;  for  the  appar¬ 
ent  exceptions  to  the  rule  are  so  few  that  they  may  fairly 
be  attributed  to  our  not  having  as  yet  discovered  in  an 
intermediate  deposit  certain  forms  which  are  absent  in  it, 
but  which  occur  both  above  and  below:  so  in  space,  it  cer¬ 
tainly  is  the  general  rule  that  the  area  inhabited  by  a 
single  species,  or  by  a  group  of  species,  is  continuous,  and 


SUMMARY. 


42? 

the  exceptions,  which  are  not  rare,  may,  as  I  have 
attempted  to  show,  be  accounted  for  by  former  migrations 
under  ditferent  circumstances,  or  through  occasional  means 
of  transport,  or  by  the  species  having  become  extinct  in 
the  intermediate  tracts.  Both  in  time  and  space  species 
and  groups  of  species  have  their  points  of  maximum 
development.  Groups  of  species,  living  during  the  same 
period  of  time,  or  living  within  the  same  area,  are  often 
characterized  by  trifling  features  in  common,  as  of  sculpt¬ 
ure  or  color.  In  looking  to  the  long  succession  of  past 
ages,  as  in  looking  to  distant  provinces  throughout  the 
world,  we  find  that,  species  in  certain  classes  differ  little 
from  each  other,  while  those  in  another  class,  or  only  in  a 
different  section  of  the  same  order,  differ  greatly  from 
each  other.  In  both  time  and  space  the  lowly  organized 
members  of  each  class  generally  change  less  than  the 
highly  organized;  but  there  are  in  both  cases  marked 
exceptions  to  the  rule.  According  to  our  theory,  these 
several  relations  throughout  time  and  space  are  intelligible; 
for  whether  we  look  to  the  allied  forms  of  life  which  have 
changed  during  successive  ages,  or  to  those  which  have 
changed  after  having  migrated  into  distant  quarters,  in 
both  cases  they  are  connected  by  the  same  bond  of  ordinary 
generation;  in  both  cases  the  laws  of  variation  have  been 
the  same,  and  modifications  have  been  accumulated  by  the 
same  means  of  natural  selection. 


m 


CLASSIFICATION. 


CHAPTER  XIV. 

MUTUAL  AFFINITIES  OF  ORGANIC  BEINGS:  MORPHOLOGY — 
EMBRYOLOGY — RUDIMENTARY  ORGANS. 

Classification,  groups  subordinate  to  groups — Natural  system — Rules 
and  difficulties  in  classification,  explained  on  tbe  theory  of 
descent  with  modification — Classification  of  varieties — Descent 
always  used  in  classification — Analogical  or  adaptive  characters— 
Affinities,  general,  complex  and  radiating — Extinction  separates 
and  defines  groups — Morphology,  between  members  of  the  same 
class,  between  parts  of  the  same  individual — Embryology,  laws 
of,  explained  by  variations  not  supervening  at  an  early  age,  and 
being  inherited  at  a  corresponding  age — Rudimentary  organs, 
their  origin  explained — Summary. 

CLASSIFICATION. 

From  the  most  remote  period  in  the  history  of  the  world 
organic  beings  have  been  found  to  resemble  each  other  in 
descending  degrees,  so  that  they  can  be  classed  in  groups 
under  groups.  This  classification  is  not  arbitrary  like  the 
grouping  of  the  stars  in  constellations.  The  existence  of 
groups  would  have  been  of  simple  significance,  if  one  group 
had  been  exclusively  fitted  to  inhabit  the  land,  and  another 
the  water;  one  to  feed  on  flesh,  another  on  vegetable 
matter,  and  so  on;  but  the  case  is  widely  different,  for  it  is 
notorious  how  commonly  members  of  even  the  same  sub¬ 
group  have  different  habits.  In  the  second  and  fourth 
chapters,  on  Variation  and  on  Natural  Selection,  I  have 
attempted  to  show  that  within  each  country  it  is  the  widely 
ranging,  the  much  diffused  and  common,  that  is  the 
dominant  species,  belonging  to  the  larger  genera  in  each 
class,  which  vary  most.  The  varieties,  or  incipient  species, 
thus  produced,  ultimately  become  converted  into  new  and 
distinct  species;  and  these,  on  the  principle  of  inheritance, 
tend  to  produce  other  new  and  dominant  species.  Conse- 


CLASSIFICA  TIOFT. 


429 


quently  the  groups  which  are  now  large,  and  which  gen¬ 
erally  include  many  dominant  species,  tend  to  go  on  in¬ 
creasing  in  size.  I  further  attempted  to  show  that  from 
the  varying  descendants  of  each  species  trying  to  occupy 
as  many  and  as  different  places  as  possible  in  the  economy 
of  natuie,  they  constantly  tend  to  diverge  in  character. 
This  latter  conclusion  is  supported  by  observing  the  great 
diversity  of  forms,  which,  in  any  small  area,  come  into  the 
closest  competition,  and  by  certain  facts  in  naturalization. 

.  attempted  also  to  show  that  there  is  a  steady  tendency 
in  the  forms  which  are  increasing  in  number  and  diverging 
in  character,  to  supplant  and  exterminate  the  preceding, 
less  divergent  and  less  improved  forms.  I  request  the 
reader  to  turn  to  the  diagram  illustrating  the  action,  as 
formerly  explained,  of  these  several  principles;  and  he  will 
see  that  the  inevitable  result  is,  that  the  modified  descend¬ 
ants  proceeding  from  one  progenitor  become  broken  up  into 
groups  subordinate  to  groups.  In  the  diagram  each  letter 
on  the  uppermost  line  may  represent  a  genus  including 
several  species;  and  the  whole  of  the  genera  along  this 
upper  line  form  together  one  class,  for  all  are  descended 
from  one  ancient  parent,  and,  consequently,  have  inherited 
something  in  common.  But  the  three  genera  on  the  left 
hand  have,  on  this  same  principle,  much  in  common,  and 
form  a  subfamily,  distinct  from  that  containing  the  next 
two  genera  on  the  right  hand,  which  diverged  from  a  com¬ 
mon  parent  at  the  fifth  stage  of  descent.  These  five  genera 
have  also  much  in  common,  though  less  than  when  grouped 
in  subfamilies;  and  they  form  a  family  distinct  from  that 
containing  the  three  genera  still  further  to  the  right  hand, 
which  diverged  at  an  earlier  period.  And  all  these  genera' 
descended  from  (A),  form  an  order  distinct  from  the  genera 
descended  from  (I).  So  that  we  here  have  many  species 
descended  from  a  single  progenitor  grouped  into  genera; 
and  the  genera  into  subfamilies,  families  and  orders,  all 
under  one  great  class.  The  grand  fact  of  the  natural  sub¬ 
ordination  of  organic  beings  in  groups  under  groups, 
which,  from  its  familiarity,  does  not  always  sufficiently 
strike  us,  is  in  my  judgment  thus  explained.  No  doubt 
organic  beings,  like  all  other  objects,  can  be  classed  in  many 
ways,  either  artificially  by  single  characters,  or  more  natu¬ 
rally  by  a  number  of  characters.  We  know,  for  instance, 


430  CLASSIFICATION. 

that  minerals  and  the  elemental  substances  can  be  thus 
arranged.  In  this  case  there  is  of  course  no  relation  to 
o-enealogical  succession,  and  no  cause  can  at  present  be 
assigned  for  their  falling  into  groups.  But  with  organic 
beings  the  case  is  different,  and  the  view  above  given 
accords  with  their  natural  arrangement  m  group  under 
group;  and  no  other  explanation  has  ever  been  attempted. 

Naturalists,  as  we  have  seen,  try  to  arrange  the  species, 
genera  and  families  in  each  class,  on  what  is  called  the 
Natural  System.  But  what  is  meant  by  this  system. 
Some  authors  look  at  it  merely  as  a  scheme  foi  arranging 
together  those  living  objects  which  are  most  alike,  and 
for  separating  those  which  are  most  unlike;  or  as  an 
artificial  method  of  enunciating,  as  briefly  as  possible,  gen¬ 
eral  propositions — that  is,  by  one  sentence  to  give  the  chai- 
acters  common,  for  instance,  to  all  mammals,  by  another 
those  common  to  all  carnivora,  by  another  those  common 
to  the  dog-genus,  and  then,  by  adding  a  single  sentence,  a 
full  description  is  given  of  each  kind  of  dog.  I  he  in¬ 

genuity  and  utility  of  this  system  are  indisputable.  But 
many  naturalists  think  that  something  more  is  meant  by 
the  Natural  System;  they  believe  that  it  reveals  the  plan 
of  the  Creator;  but  unless  it  be  specified  whether  order  m 
time  or  space,  or  both,  or  what  else  is  meant  by  the  Pja^ 
of  the  Creator,  it  seems  to  me  that  nothing  is  thus  added 
to  our  knowledge.  Expressions  such  as  that  famous  ono 
by  Linn  sens,  which  we  often  meet  with  in  a  moie  or  less 
concealed  form,  namely,  that  the  characters  do  not  make 
the  genus,  but  that  the  genus  gives  the  characters,  seem  to 
imply  that  some  deeper  bond  is  included  in  our  classifica¬ 
tions  than  mere  resemblance.  I  believe  that  this  is  the 
case,  and  that  community  of  descent— the  one  known 
cause  of  close  similarity  in  organic  beings  is  the  bond, 
which,  though  observed^ by  various  degrees  of  modification, 
is  partially  revealed  to  us  by  our  classifications. 

Let  us  now  consider  the  rules  followed  in  classification, 
and  the  difficulties  which  are  encountered  on  the  view  that 
classification  either  gives  some  unknown  plan  of  creation, 
or  is  simply  a  scheme  for  enunciating  general  propositions 
and  of  placing  together  the  forms  most  like  each  other. 
It  might  have  been  thought  (and  was  in  ancient  times 
thought)  that  those  parts  of  the  structure  which  deter- 


CLASSIFICA  TIOJST. 


431 


mined.  the  habits  of  life,  and  the  general  place  of  each 
being  in  the  economy  of  nature,  would  be  of  very  high  im¬ 
portance  in  classification.  Nothing  can  be  more  false. 
No  one  regards  the  external  similarity  of  a  mouse  to  a 
shrew,  of  a  dugong  to  a  whale,  of  a  whale  to  a  fish,  as  of 
any  importance.  These  resemblances,  though  so  inti¬ 
mately  connected  with  the  whole  life  of  the  being,  are 
ranked  as  merely  “adaptive  or  analogical  characters;”  but 
to  the  consideration  of  these  resemblances  we  shall  recur. 
It  may  even  be  given  as  a  general  rule,  that  the  less  any 
part  of  the  organization  is  concerned  with  special  habits, 
the  more  important  it  becomes  for  classification.  As  an 
instance:  Owen,  in  speaking  of  the  dugong,  says,  “The 
generative  organs,  being  those  which  are  most  remotely 
related  to  the  habits  and  food  of  an  animal,  I  have  always 
regarded  as  affording  very  clear  indications  of  its  true  affin¬ 
ities.  We  are  least  likely  in  the  modifications  of  these 
organs  to  mistake  a  merely  adaptive  for  an  essential  char¬ 
acter.”  With  plants  how  remarkable  it  is  that  the  organs 
of  vegetation,  on  which  their  nutrition  and  life  depend, 
are  of  little  signification;  whereas  the  organs  of  reproduc¬ 
tion,  with  their  product  the  seed  and  embryo,  are  of  para¬ 
mount  importance!  So  again,  in  formerly  discussing  cer¬ 
tain  morphological  characters  which  are  not  functionally 
important,  we  have  seen  that  they  are  often  of  the  highest 
service  in  classification.  This  depends  on  their  constancy 
throughout  many  allied  groups;  and  their  constancy 
chiefly  depends  on  any  slight  deviations  not  having  been 
preserved  and  accumulated  by  natural  selection,  which 
acts  only  on  serviceable  characters. 

That  the  mere  physiological  importance  of  an  organ 
does  not  determine  its  classificatory  value,  is  almost 
proved  by  the  fact,  that  in  allied  groups,  in  which  the 
same  organ,  as  we  have  every  reason  to  suppose,  has  nearly 
the  same  physiological  value,  its  classificatory  value  is 
widely  different.  No  naturalist  can  have  worked  long  at 
any  group  without  being  struck  with  this  fact;  and  it  has 
been  fully  acknowledged  in  the  writings  of  almost  every 
author.  It  will  suffice  to  quote  the  highest  authority, 
Robert  Brown,  who,  in  speaking  of  certain  organs  in  the 
Proteaceae,  says  their  generic  importance,  “  like  that  of  all 
their  parts,  not  only  in  this,  but,  as  I  apprehend  in  every 


432 


CLASSIFICATION. 


natural  family,  is  very  unequal,  and  in  some?  cases  seems  to 
be  entirely  lost.”  Again,  in  another  work  he  says,  the 
genera  of  the  Connaracese  “  differ  in  having  one  or  more 
ovaria,  in  the  existence  or  absence  of  albumen,  in  the  im¬ 
bricate  or  valvular  aestivation.  Any  one  of  these  charac¬ 
ters  singly  is  frequently  of  more  than  generic  importance, 

,  though  here  even,  when  all  taken  together,  they  appear  in- 
i  sufficient  to  separate  Onestis  from  Oonnarus.”  To  give  ail 
example  among  insects:  in  one  great  division  of  the  Hy- 
menoptera,  the  antennae,  as  Westwood  has  remarked,  are 
most  constant  in  structure;  in  another  division  they  differ 
much,  and  the  differences  are  of  quite  subordinate  value 
in  classification;  yet  no  one  will  say  that  the  antennae  in 
these  two  divisions  of  the  same  order  are  of  unequal  physi¬ 
ological  importance.  Any  number  of  instances  could  be 
given  of  the  varying  importance  for  classification  of  the 
same  important  organ  within  the  same  group  of  beings. 

Again,  no  one  will  say  that  rudimentary  or  atrophied 
organs  are  of  high  physiological  or  vital  importance;  yet, 
undoubtedly,  organs  in  this  condition  are  often  of  much 
value  in  classification.  No  one  will  dispute  that  the  rudi¬ 
mentary  teeth  in  the  upper  jaws  of  young  ruminants,  and 
certain  rudimentary  bones  of  the  leg,  are  highly  serviceable 
in  exhibiting  the  close  affinity  between  ruminants  and 
pachyderms.  Robert  Brown  has  strongly  insisted  on  the 
fact  that  the  position  of  the  rudimentary  florets  is  of  the 
highest  importance  in  the  classification  of  the  grasses. 

Numerous  instances  could  be  given  of  characters  derived 
from  parts  which  must  be  considered  of  very  trifling  physi¬ 
ological  importance,  but  which  are  universally  admitted  as 
highly  serviceable  in  the  definition  of  whole  groups.  For 
instance,  whether  or  not  there  is  an  open  passage  from  the 
nostrils  to  the  mouth,  the  only  character,  according  to 
Owen,  which  absolutely  distinguishes  fishes  and  reptiles — - 
the  inflection  of  the  angle  of  the  lower  jaw  in  Marsupials — 
the  manner  in  which  the  wings  of  insects  are  folded — mere 
color  in  certain  Algae — mere  pubescence  on  parts  of  the 
flower  in  grasses — the  nature  of  the  dermal  covering,  as 
hair  or  feathers,  in  the  Yertebrata.  If  the  Ornithorhyn- 
chus  had  been  covered  with  feathers  instead  of  hair,  this 
external  and  trifling  character  would  have  been  considered 
by  naturalists  as  an  important  aid  in  determining  the  de¬ 
gree  of  affinity  of  this  strange  creature  to  birds. 


CLASSIFICATION. 


433 


The  importance,  for  classification,  of  trifling  characters, 
mainly  depends  on  their  being  correlated  with  many  other 
characters  of  more  or  less  importance.  The  value  indeed 
of  an  aggregate  of  characters  is  very  evident  in  natural  his¬ 
tory.  Hence,  as  has  often  been  remarked,  a  species  may 
depart  from  its  allies  in  several  characters,  both  of  high 
physiological  importance,  and  of  almost  universal  preva¬ 
lence,  and  yet  leave  us  in  no  doubt  where  it  should 
be  ranked.  Hence,  also,  it  has  been  found  that  a 
classification  founded  on  any  single  character,  however 
important  that  may  be,  has  always  failed;  for  no  part  of 
the  organization  is  invariably  constant.  The  importance 
of  an  aggregate  of  characters,  even  when  none  are  impor¬ 
tant,  alone  explains  the  aphorism  enunciated  by  Linnaeus, 
namely,  that  the  characters  do  not  give  the  genus,  but  the 
genus  gives  the  character;  for  this  seems  founded  on  the 
appreciation  of  many  trifling  points  of  resemblance,  too 
slight  to  be  defined.  Certain  plants,  belonging  to  the 
Malpighiaceae,  bear  perfect  and  degraded  flowers;  in  the 
latter,  as  A.  de  Jussieu  has  remarked,  “  The  greater  num¬ 
ber  of  the  characters  proper  to  the  species,  to  the  genus, 
to  the  family,  to  the  class,  disappear,  and  thus  laugh  at 
our  classification.”  When  Aspicarpa  produced  in  France, 
during  several  years,  only  these  degraded  flowers,  depart¬ 
ing  so  wonderfully  in  a  number  of  the  most  important 
points  of  structure  from  the  proper  type  of  the  order,  yet 
M.  Richard  sagaciously  saw,  as  Jussieu  observes,  that  this 
genus  should  still  be  retained  among  the  Malpighiaceae. 
This  case  well  illustrates  the  spirit  of  our  classifications. 

Practically,  when  naturalists  are  at  work,  they  do  not 
trouble  themselves  about  the  physiological  value  of  the 
characters  which  they  use  in  defining  a  group  or  in  allo¬ 
cating  any  particular  species.  If  they  find  a  character 
nearly  uniform,  and  common  to  a  great  number  of  forms, 
and  not  common  to  others,  they  use  it  as  one  of  high 
value;  if  common  to  some  lesser  number,  they  use  it  as  of 
subordinate  value.  This  principle  has  been  broadly  con¬ 
fessed  by  some  naturalists  to  be  the  true  one;  and  by  none 
more  clearly  than  by  that  excellent  botanist,  Aug.  !3L 
Hilaire.  If  several  trifling  characters  are  always  found  in 
combination,  though  no  apparent  bond  of  connection  can 
be  discovered  between  them,  especial  value  is  set  on  them 


434 


CLASSIFICA  TIOtf. 


As  in  most  groups  of  animals,  important  organs,  such  as 
those  for  propelling  the  blood,  or  for  aerating  it,  or  those 
for  propagating  the  race,  are  found  nearly  uniform,  they 
are  considered  as  highly  serviceable  in  classification;  but  in 
some  groups  all  these,  the  most  important  vital  organs,  are 
found  to  offer  characters  of  quite  subordinate  value.  Thus, 
as  Fritz  Muller  has  lately  remarked,  in  the  same  group  of 
crustaceans,  Cypridina  is  furnished  with  a  heart,  while  in 
two  closely  allied  genera,  namely  Cypris  and  Cytherea, 
there  is  no  such  organ;  one  species  of  Cypridina  has  well- 
developed  branchiae,  while  another  species  is  destitute  of 
them. 

We  can  see  why  characters  derived  from  the  embryo 
should  be  of  equal  importance  with  those  derived  from  the 
adult,  for  a  natural  classification  of  course  includes  all 
ages.  But  it  is  by  no  means  obvious,  on  the  ordinary 
view,  why  the  structure  of  the  embryo  should  be  more  im¬ 
portant  for  this  purpose  than  that  of  the  adult,  which 
alone  plays  its  full  part  in  the  economy  of  nature.  Yet  it 
has  been  strongly  urged  by  those  great  naturalists,  Milne 
Edwards  and  Agassiz,  that  embryological  characters  are 
the  most  important  of  all;  and  this  doctrine  has  very  gen¬ 
erally  been  admitted  as  true.  Nevertheless,  their  impor¬ 
tance  has  sometimes  been  exaggerated,  owing  to  the  adap¬ 
tive  characters  of  larvae  not  having  been  excluded;  in  order 
to  show  this,  Fritz  Muller  arranged,  by  the  aid  of  such 
characters  alone,  the  great  class  of  crustaceans,  and  the  ar¬ 
rangement  did  not  prove  a  natural  one.  But  there  can  be 
no  doubt  that  embryonic,  excluding  larval  characters,  are 
of  the  highest  value  for  classification,  not  only  with  animals 
but  with  plants.  Thus  the  main  divisions  of  flowering 
plants  are  founded  on  differences  in  the  embryo — on  the 
number  and  position  of  the  cotyledons,  and  on  the  mode  of 
development  of  the  plumule  and  radicle.  We  shall  im¬ 
mediately  see  why  these  characters  possess  so  high  a  value 
in  classification,  namely,  from  the  natural  system  being 
genealogical  in  its  arrangement. 

Our  classifications  are  often  plainly  influenced  by  chains 
of  affinities.  Nothing  can  be  easier  than  to  define  a 
number  of  characters  common  to  all  birds;  but  with 
crustaceans,  any  such  definition  has  hitherto  been  found 
impossible.  There  are  crustaceans  at  the  opposite  ends  of 


CLASSIFICATION. 


435 

the  series,  which  have  hardly  a  character  in  common;  yet 
the  species  at  both  ends,  from  being  plainly  allied  to  others, 
and  these  to  others,  and  so  onward,  can  be  recognized  as 
unequivocally  belonging  to  this,  and  to  no  other  class  of 
the  Articulata. 

Geographical  distribution  has  often  been  used,  though 
perhaps  not  quite  logically,  in  classification,  more  espec¬ 
ially  in  very  large  groups  of  closely  allied  forms.  Tem- 
minck  insists  on  the  utility  or  even  necessity  of  this 
practice  in  certain  groups  of  birds;  and  it  has  been  fol¬ 
lowed  by  several  entomologists  and  botanists. 

Finally,  with  respect  to  the  comparative  value  of  the 
various  groups  of  species,  such  as  orders,  suborders,  fam¬ 
ilies,  subfamilies,  and  genera,  they  seem  to  be,  at  least  at 
present,  almost  arbitrary.  Several  of  the  best  botanists, 
such  as  Mr.  Bentham  and  others,  have  strongly  insisted  on 
their  arbitrary  value.  Instances  could  be  given  among 
plants  and  insects,  of  a  group  first  ranked  by  practiced 
naturalists  as  only  a  genus,  and  then  raised  to  the  rank  of 
a  subfamily  or  family;  and  this  has  been  done,  not  be¬ 
cause  further  research  has  detected  important  structural 
differences,  at  first  overlooked,  but  because  numerous  allied 
species,  with  slightly  different  grades  of  deference,  hav<j 
been  subsequently  discovered. 

.  All  the  foregoing  rules  and  aids  and  difficulties  in  clas^ 
sification  may  be  explained,  if  I  do  not  greatly  deceive 
myself,  on  the  view  that  the  Natural  System  is  founded  on 
descent  with  .modification— that  the  characters  which 
naturalists  consider  as  showing  true  affinity  between  any 
two  or  more  species,  are  those  which  have  'been  inherited 
from  a  common  parent,  all  true  classification  being  genea. 
logical— that  community  of  descent  is  the  hidden  bond 
which  naturalists  have  been  unconsciously  seeking,  and  not 
some  unknown  plan  of  creation,  or  the  enunciation  of 
general,  propositions,  and  the  mere  putting  together  and 
separating  objects  more  or  less  alike. 

But  I  must  explain  my  meaning  more  fully.  I  believe 
that  the  arrangement  of  the  groups  within  each  class,  in 
due  subordination  and  relation  to  each  other,  must  be 
strictly  genealogical  in  order  to  be  natural;  but  that  the 
amount  of  difference  in  the  several  branches  or  groups, 
though  allied  in  the  same  degree  in  blood  to  their 


436 


CLASSIFIGA  TION. 


common  progenitor,  may  differ  greatly,  being  due  to 
the  different  degrees  of  modification  which  they  have 
undergone ;  and  this  is  expressed  by  the  forms  being 
ranked  under  different  genera,  families,  sections  or 
orders.  The  reader  will  best  understand  what  is  meant, 
if  he  will  take  the  trouble  to  refer  to  the  diagram  in 
the  fourth  chapter.  We  will  suppose  the  letters  A  to 
L  to  represent  allied  genera  existing  during  the  Silurian 
epoch,  and  descended  from  some  still  earlier  form.  In 
three  of  these  genera  (A,  F  and  I),  a  species  has  trans¬ 
mitted  modified  descendants  to  the  present  day,  repre¬ 
sented  by  the  fifteen  genera  (a1 4  to  z14)  on  the  uppermost 
horizontal  line.  Now,  all  these  modified  descendants  from 
a  single  species  are  related  in  blood  or  descent  in  the  same 
degree.  They  may  metaphorically  be  called  cousins  to  the 
same  millionth  degree,  yet  they  differ  widely  and  in  dif¬ 
ferent  degrees  from  each  other.  The  forms  descended 
from  A,  now  broken  up  into  two  or  three  families,  consti¬ 
tute  a  distinct  order  from  those  descended  from  I,  also 
broken  up  into  two  families.  Nor  can  the  existing  species 
descended  from  A  be  ranked  in  the  same  genus  with  the 
parent  A,  or  those  from  I  with  parent  I.  But  the  existing 
genus  f14  may  be  supposed  to  have  been  but  slightly  mod¬ 
ified,  and  it  will  then  rank  with  the  parent  genus  F,  just 
as  some  few  still  living  organisms  belong  to  Silurian  genera. 
So  that  the  comparative  value  of  the  differences  between 
these  organic  beings,  which  are  all  related  to  each  other  in 
the  same  degree  in  blood,  has  come  to  be  widely  different. 
Nevertheless,  their  genealogical  arrangement  remains 
strictly  true,  not  only  at  the  present  time,  but  at  each  suc¬ 
cessive  period  of  descent.  All  the  modified  descendants 
from  A  will  have  inherited  something  in  common  from 
their  common  parent,  as  will  all  the  descendants  from  I; 
s©  will  it  be  with  each  subordinate  branch  of  descendants 
at  each  successive  stage.  If,  however,  we  suppose  any  de¬ 
scendant  of  A  or  of  I  to  have  become  so  much  modified  as 
to  have  lost  all  traces  of  its  parentage  in  this  case,  its  place 
in  the  natural  system  will  be  lost,  as  seems  to  have 
occurred  with  some  few  existing  organisms.  All  the 
descendants  of  the  genus  F,  along  its  whole  line  of 
descent,  are  supposed  to  have  been  but  little  modi¬ 
fied,  and  they  form  a  single  genus.  But  this  genus, 


CLASSIFICA  TION. 


437 


though  much  isolated,  will  still  occupy  its  proper  interme¬ 
diate  position.  The  representation  of  the  groups,  as  here 
given  in  the  diagram  on  a  flat  surface,  is  much  too  simple. 
The  branches  ought  to  have  diverged  in  all  directions.  If 
the  names  of  the  groups  had  been  simply  written  down  in 
a  linear  series  the  representation  would  have  been  still  less 
natural;  and  it  is  notoriously  not  possible  to  represent  in  a 
series,  on  a  flat  surface,  the  affinities  which  we  discover  in 
nature  among  the  beings  of  the  same  group.  Thus,  the 
natural  system  is  genealogical  in  its  arrangement,  like  a 
pedigree.  But  the  amount  of  modification  which  the  dif- 
erent  groups  have  undergone  has  to  be  expressed  by  rank¬ 
ing  them  under  different  so-called  genera,  subfamilies, 
families,  sections,  orders  and  classes. 

It  may  be  worth  while  to  illustrate  this  view  of  classifi¬ 
cation,  by  taking  the  case  of  languages.  If  we  possessed 
a  perfect  pedigree  of  mankind,  a  genealogical  arrangement 
of  the  races  of  man  would  afford  the  best  classification  of 
the  various  languages  now  spoken  throughout  the  world; 
and  if  all  extinct  languages,  and  all  intermediate  and 
slowly  changing  dialects,  were  to  be  included,  such  an 
arrangement  would  be  the  only  possible  one.  Yet  it  might 
be  that  some  ancient  languages  had  altered  very  little  and 
had  given  rise  to  few  new  languages,  while  others  had 
altered  much  owing  to  the  spreading,  isolation  and  state  of 
civilization  of  the  several  co-descended  races,  and  had  thus 
given  rise  to  many  new  dialects  and  languages.  The 
various  degrees  of  difference  between  the  languages  of  the 
same  stock  would  have  to  be  expressed  by  groups  sub¬ 
ordinate  to  groups;  but  the  proper  or  even  the  only  possi¬ 
ble  arrangement  would  still  be  genealogical;  and  this 
would  be  strictly  natural,  as  it  would  connect  together  all 
languages,  extinct  and  recent,  by  the  closest  affinities, 
and  would  give  the  filiation  and  origin  of  each  tongue. 

In  confirmation  of  this  view,  let  us  glance  at  the  classifi¬ 
cation  of  varieties,  which  are  known  or  believed  to  be  des¬ 
cended  from  a  single  species.  These  are  grouped  under 
the  species,  with  the  subvarieties  under  the  varieties;  and 
in  some  cases,  as  with  the  domestic  pigeon,  with  several 
other  grades  of  difference.  Nearly  the  same  rules  are  fol¬ 
lowed  as  in  classifying  species.  Authors  have  insisted  on 
the  necessity  of  arranging  varieties  on  a  natural  instead  of 


438 


CLASSIFICATION. 


an  artificial  system;  we  are  cautioned,  for  instance,  not  to 
class  two  varieties  of  the  pine-apple  together,  merely  be¬ 
cause  their  fruit,  though  the  most  important  part,  happens 
to  be  nearly  identical;  no  one  puts  the  Swedish  and  com¬ 
mon  turnip  together,  though  the  esculent  and  thickened 
stems  are  so  similar.  Whatever  part  is  found  to  be  most 
constant,  is  used  in  classing  varieties:  thus  the  great  agri¬ 
culturist  Marshall  says  the  horns  are  very  useful  for  this 
purpose  with  cattle,  because  they  are  less  variable  than  the 
shape  or  color  of  the  body,  etc. ;  whereas  with  sheep  the 
horns  are  much  less  serviceable,  because  less  constant.  In 
classing  varieties,  I  apprehend  that  if  we  had  a  real  pedi¬ 
gree,  a  genealogical  classification  would  be  universally  pre¬ 
ferred;  and  it  has  been  attempted  in  some  cases.  For  we 
might  feel  sure,  whether  there  had  been  more  or  less  modi¬ 
fication,  that  the  principle  of  inheritance  would  keep  the 
forms  together  which  were  allied  in  the  greatest  number  of 
points.  In  tumbler  pigeons,  though  some  of  the  sub- 
varieties  differ  in  the  important  character  of  the  length  of 
the  beak,  yet  all  are  kept  together  from  having  the  common 
habit  of  tumbling:  but  the  short-faced  breed  has  nearly  or 
quite  lost  this  habit:  nevertheless,  without  any  thought  on 
the  subject,  these  tumblers  are  kept  in  the  same  group, 
because  allied  in  blood  and  alike  in  some  other  respects.  . 

With  species  in  a  state  of  nature,  every  naturalist  has  in 
fact  brought  descent  into  his  classification;  for  he  includes 
in  his  lowest  grade,  that  of  species,  the  two  sexes;  and  how 
enormously  these  sometimes  differ  in  the  most  important 
characters  is  known  to  every  naturalist:  scarcely  a  single 
fact  can  be  predicated  in  common  of  the  adult  males  and 
hermaphrodites  of  certain  cirripedes,  and  yet  no  one 
dreams  of  separating  them.  As  soon  as  the  three  Orchi- 
dean  forms,  Monachanthus,  Myanthus,  and  Catasetum, 
which  had  previously  been  ranked  as  three  distinct  genera; 
were  known  to  be  sometimes  produced  on  the  same  plant, 
they  were  immediately  considered  as  varieties;  and  now  I 
have  been  able  to  show  that  they  are  the  male,  female,  and 
hermaphrodite  forms  of  the  same  species.  The  naturalist 
includes  as  one  species  the  various  larval  stages  of  the  same 
individual,  however  much  they  may  differ  from  each  other 
and  from  the  adult,  as  well  as  the  so-called  alternate  gen¬ 
erations  of  Steenstrup,  which  can  only  in  a  technical  sense 


CLASSIFIGA  TION. 


439 


be  considered  as  the  same  individual.  He  includes  mon¬ 
sters  and  varieties,  not  from  their  partial  resemblance  to 
the  parent-form,  but  because  they  are  descended  from  it. 

As  descent  has  universally  been  used  in  classing  to¬ 
gether  the  individuals  of  the  same  species,  though  the 
males  and  females  and  lame  are  sometimes  extremely 
different;  and  as  it  has  been  used  in  classing  varieties 
which  have  undergone  a  certain,  and  sometimes  a  consid¬ 
erable  amount  of  modification,  may  not  this  same  element 
of  descent  have  been  unconsciously  used  in  grouping 
species  under  genera,  and  genera  under  higher  groups,  all 
under  the  so-called  natural  system?  I  believe  it  has  been 
unconsciously  used;  and  thus  only  can  I  understand  the 
several  rules  and  guides  which  have  been  followed  by  our 
best  systematists.  As  we  have  no  written  pedigrees,  we 
are  forced  to  trace  community  of  descent  by  resemblances 
of  any  kind.  Therefore,  we  choose  those  characters  which 
are  the  least  likely  to  have  been  modified,  in  relation  to 
the  conditions  of  life  to  which  each  species  has  been  recently 
exposed.  Rudimentary  structures  on  this  view  are  as  good, 
as,  or  even  sometimes  better  than  other  parts  of  the  organ¬ 
ization.  We  care  not  how  trifling  a  character  may  be — let 
it  be  the  mere  inflection  of  the  angle  of  the  jaw,  the  manner 
in  which  an  insect’s  wing  is  folded,  whether  the  skin  be 
covered  by  hair  or  feathers — if  it  prevail  throughout  many 
and  different  species,  especially  those  having  very  different 
habits  of  life,  it  assumes  high  value;  for  we  can  account  for 
its  presence  in  so  many  forms  with  such  different  habits, 
only  by  inheritance  from  a  common  parent.  We  may  err 
in  this  respect  in  regard  to  single  points  of  structure,  but 
when  several  characters,  let  them  be  ever  so  trifling, 
concur  throughout  a  large  group  of  beings  having  different 
habits,  we  may  feel  almost  sure,  on  the  theory  of  descent, 
that  these  characters  have  been  inherited  from  a  common 
ancestor;  and  we  know  that  such  aggregated  characters 
have  especial  value  in  classification. 

We  can  understand  why  a  species  or  a  group  of  species 
may  depart  from  its  allie j,  in  several  of  its  most  important 
characteristics,  and  yet  be  safely  classed  with  them.  This 
may  be  safely  done,  and  is  often  done,  as  long  as  a  suffi¬ 
cient  number  of  characters,  let  them  be  ever  so  unimpor¬ 
tant,  betrays  the  hidden  bond  of  community  of  descent. 


440 


ANALOGICAL  RESEMBLANCES. 


Let  two  forms  have  not  a  single  character  in  common,  yet, 
if  these  extreme  forms  are  connected  together  by  a  chain 
of  intermediate  groups,  we  may  at  once  infer  their  com¬ 
munity  of  descent,  and  we  put  them  all  into  the  same 
class.  "  As  we  find  organs  of  high  physiological  impor¬ 
tance — those  which  serve  to  preserve  life  under  the  most 
diverse  conditions  of  existence — are  generally  the  most 
constant,  we  attach  especial  value  to  them;  but  if  these 
same  organs,  in  another  group  or  section  of  a  group,  are 
found  to  differ  much,  we  at  once  value  them  less  in  our 
classification.  We  shall  presently  see  why  embryological 
characters  are  of  such  high  classificatory  importance. 
Geographical  distribution  may  sometimes  be  brought  use¬ 
fully  into  play  in  classing  large  genera,  because  all  the 
species  of  the  same  genus,  inhabiting  any  distinct  and 
isolated  region,  are  in  all  probability  descended  from  the 
same  parents. 

ANALOGICAL  RESEMBLANCES. 

We  can  understand,  on  the  above  views,  the  very  impor¬ 
tant  distinction  between  real  affinities  and  analogical  or 
adaptive  resemblances.  Lamarck  first  called  attention  to 
this  subject,  and  he  has  been  ably  followed  by  Macleayand 
others.  The  resemblance  in  the  shape  of  the  body  and  in 
the  fin-like  anterior  limbs  between  dugongs  and  whales,  and 
between  these  two  orders  of  mammals  and  fishes,  are  ana¬ 
logical.  So  is  the  resemblance  between  a  mouse  and  a 
shrew-mouse  (Sorex),  which  belong  to  different  orders' 
and  the  still  closer  resemblance,  insisted  on  by  Mr.  Mivart. 
between  the  mouse  and  a  small  marsupial  animal  (Antech* 
in  us)  of  Australia.  These  latter  resemblances  may  be 
accounted  for,  as  it  seems  to  me,  by  adaptation  for  similarly 
active  movements  through  thickets  and  herbage,  togethei 
with  concealment  from  enemies. 

Among  insects  there  are  innumerable  similar  instances; 
thus  Linnaeus,  misled  by  external  appearances,  actually 
classed  an  homopterous  insect  as  a  moth.  We  see  some¬ 
thing  of  the  same  kind  even  with  our  domestic  varieties, 
as  in  the  strikingly  similar  shape  of  the  body  in  the  im¬ 
proved  breeds  of  the  Chinese  and  common  pig,  which  are 
descended  from  distinct  species;  and  in  the  similarly  thick- 


ANALOGICAL  RESEMBLANCES. 


441 


ened  stems  of  the  common  and  specifically  distinct  Swedish 
turnip.  The  resemblance  between  the  greyhound  and  the 
race-horse  is  hardly  more  fanciful  than  the  analogies  which 
have  been  drawn  by  some  authors  between  widely  different 
animals. 

On  the  view  of  characters  being  of  real  importance  for 
classification,  only  in  so  far  as  they  reveal  descent,  we  can 
clearly  understand  why  analogical  or  adaptive  characters, 
although  of  the  utmost  importance  to  the  welfare  of  the 
being,  are  almost  valueless  to  the  systematist.  For  animals, 
belonging  to  two  most  distinct  lines  of  descent,  may  have 
become  adapted  to  similar  conditions,  and  thus  have  as¬ 
sumed  a  close  externa]  resemblance;  but  such  resemblances 
will  not  reveal — will  rather  tend  to  conceal  their  blood- 
relationship.  We  can  thus  also  understand  the  apparent 
paradox,  that  the  very  same  characters  are  analogical  when 
one  group  is  compared  with  another,  but  give  true  affinities 
when  the  members  of  the  same  group  are  compared  to¬ 
gether:  thus,  the  shape  of  the  body  and  fin-like  limbs  are 
only  analogical  when  whales  are  compared  with  fishes, 
being  adaptations  in  both  classes  for  swimming  through 
the  water;  but  between  the  several  members  of  the  whale 
family,  the  shape  of  the  body  and  the  fin-like  limbs  offer 
characters  exhibiting  true  affinity;  for  as  these  parts  are 
so  nearly  similar  throughout  the  whole  family,  we  cannot 
doubt  that  they  have  been  inherited  from  a  common  ances¬ 
tor.  So  it  is  with  fishes. 

Numerous  cases  could  be  given  of  striking  resemblances 
in  quite  distinct  beings  between  single  parts  or  organs, 
which  have  been  adapted  for  the  same  functions.  A  good 
instance  is  afforded  by  the  close  resemblance  of  the  jaws  of 
the  dog  and  Tasmanian  wolf  or  Thylacinus — animals 
which  are  widely  sundered  in  the  natural  system.  But 
this  resemblance  is  confined  to  general  appearance, 
as  in  the  prominence  of  the  canines,  and  in  the  cut¬ 
ting  shape  of  the  molar  teeth.  For  the  teeth  really 
differ  much:  thus  the  dog  has  on  each  side  of  the 
upper  jaw  four  pre-molars  and  only  two  molars;  while 
the  Thylacinus  has  three  pre-molars  and  four  molars.  The 
molars  also  differ  much  in  the  two  animals  in  relative  size 
and  structure.  The  adult  dentition  is  preceded  by  a  widely 
different  milk  dentition.  Any  one  may,  of  course,  deny 


ANALOGICAL  RESEMBLANCES. 


i42 

that  the  teeth  in  either  case  have  been  adapted  for  tearing 
flesh,  through  the  natural  selection  of  successive  variations; 
but  if  this  be  admitted  in  the  one  case,  it  is  unintelligible 
to  me  that  it  should  be  denied  in  the  other.  I  am  glad  to 
find  that  so  high  an  authority  as  Professor  Flower  has  come 
to  this  same  conclusion. 

The  extraordinary  cases  given  in  a  former  chapter,  of 
widely  different  fishes  possessing  electric  organs — of  widely 
different  insects  possessing  luminous  organs  —  and  of 
orchids  and  asclepiads  having  pollen-masses  with  viscid 
discs,  come  under  this  same  head  of  analogical  resem¬ 
blances.  But  these  cases  are  so  wonderful  that  they  were 
introduced  as  difficulties  or  objections  to  our  theory.  In 
all  such  cases  some  fundamental  difference  in  the  growth 
or  development  of  the  parts,  and  generally  in  their  matured 
structure,  can  be  detected.  The  end  gained  is  the  same, 
but  the  means,  though  appearing  superficially  to  be  the 
same,  are  essentially  different.  The  principle  formerly 
alluded  to  under  the  term  of  analogical  variation  has  prob¬ 
ably  in  these  cases  often  come  into  play;  that  is,  the  mem¬ 
bers  of  the  same  class,  although  only  distantly  allied,  have 
inherited  so  much  in  common  in  their  constitution,  that 
they  are  apt  to  vary  under  similar  exciting  causes  in  a 
similar  manner;  and  this  would  obviously  aid  in  the  ac¬ 
quirement  through  natural  selection  of  parts  or  organs, 
strikingly  like  each  other,  independently  of  their  direct 
inheritance  from  a  common  progenitor. 

As  species  belonging  to  distinct  classes  have  often  been 
adapted  by  successive  slight  modifications  to  live  under 
nearly  similar  circumstances — to  inhabit,  for  instance,  the 
three  elements  of  land,  air  and  water — we  can  perhaps 
understand  how  it  is  that  a  numerical  parallelism  has 
s<  metimes  been  observed  between  the  subgroups  of  distinct 
classes.  A  naturalist,  struck  with  a  parallelism  of  this 
nature,  by  arbitrarily  raising  or  sinking  the  value  of  the 
groups  in  several  classes  (and  all  our  experience  shows  that 
their  valuation  is  as  yet  arbitrary),  could  easily  extend  the 
parallelism  over  a  wide  range;  and  thus  the  septenary, 
quinary,  quaternary  and  ternary  classifications  have  prob¬ 
ably  arisen. 

"there  is  another  and  curious  class  of  cases  in  which 
close  external  resemblance  does  not  depend  on  adaptation 


ANALOGICAL  RESEMBLANCES. 


443 


to  similar  habits  of  life,  but  lias  been  gained  for  the  sake 
of  protection.  I  allude  to  the  wonderful  manner  in  which 
certain  butterflies  imitate,  as  first  described  by  Mr.  Bates, 
other  and  quite  distinct  species.  This  excellent  observer 
has  shown  that  in  some  districts  of  South  America,  where, 
for  instance,  an  Ithomia  abounds  in  gaudy  swarms,  an¬ 
other  butterfly,  namely,  a  Leptalis,  is  often  found  mingled 
in  the  same  flock;  and  the  latter  so  closely  resembles  the 
Ithomia  in  every  shade  and  stripe  of  color,  and  even  in  the 
shape  of  its  wings,  that  Mr.  Bates,  with  his  eyes  sharpened 
by  collecting  during  eleven  years,  was,  though  always  on 
his  guard,  continually  deceived.  When  the  mockers  and 
the  mocked  are  caught  and  compared,  they  are  found  to 
be  very  different  in  essential  structure,  and  to  belong  not 
only  to  distinct  genera,  but  often  to  distinct  families. 
Had  this  mimicry  occurred  in  only  one  or  two  instances, 
it  might  have  been  passed  over  as  a  strange  coincidence. 
But,  if  we  proceed  from  a  district  where  one  Leptalis  imi¬ 
tates  an  Ithomia,  another  mocking  and  mocked  species,  be¬ 
longing  to  the  same  two  genera,  equally  close  in  their 
resemblance,  may  be  found.  Altogether  no  less  than  ten 
genera  are  enumerated,  which  include  species  that  imitate 
other  butterflies.  The  mockers  and  mocked  always  in¬ 
habit  the  same  region;  we  never  find  an  imitator  living 
remote  from  the  form  which  it  imitates.  The  mockers  are 
almost  invariably  rare  insects;  the  mocked  in  almost  every 
case  abounds  in  swarms.  In  the  same  district  in  which  a 
species  of  Leptalis  closely  imitates  an  Ithomia,  there  are 
sometimes  other  Lepidoptera  mimicking  the  same  Ithomia: 
so  that  in  the  same  place,  species  of  three  genera  of  butter¬ 
flies  and  even  a  moth  are  found  all  closely  resembling  a 
butterfly  belonging  to  a  fourth  genus.  It  deserves  especial 
notice  that  many  of  the  mimicking  forms  of  the 
Leptalis,  as  well  as  of  the  mimicked  forms,  can  be  shown 
by  a  graduated  series  to  be  merely  varieties  of  the  same 
species;  while  others  are  undoubtedly  distinct  species. 
But  why,  it  may  be  asked,  are  certain  forms  treated  as  the 
mimicked  and  others  as  the  mimickers?  Mr.  Bates  satis¬ 
factorily  answer  this  question  by  showing  that  the  form 
which  is  imitated  keeps  the  usual  dress  of  the  group  to 
which  it  belongs,  while  the  counterfeiters  have  changed 
their  dress  and  do  not  resemble  their  nearest  allies. 


444 


ANALOGICAL  RESEMBLANCES. 


We  are  next  led  to  inquire  what  reason  can  be  assigned 
for  certain  butterflies  and  moths  so  often  assuming  tne 
dress  of  another  and  quite  distinct  form;  why,  to  the  per¬ 
plexity  of  naturalists,  has  nature  condescended  to  the 
tricks  of  the  stage?  Mr.  Bates  has,  no  doubt,  hit  on  the 
true  explanation.  The  mocked  forms,  which  always 
abound  in  numbers,  must  habitually  escape  destruction  to 
a  large  extent,  otherwise  they  could  not  exist  in  such 
swarms;  and  a  large  amount  of  evidence  has  now  been 
collected,  showing  that  they  are  distasteful  to  birds  and 
other  insect-devouring  animals.  The  mocking  forms,  on 
the  other  hand,  that  inhabit  the  same  district,  are  com¬ 
paratively  rare,  and  belong  to  rare  groups;  hence,  they 
must  suffer  habitually  from  some  danger,  for  otherwise, 
from  the  number  of  eggs  laid  by  all  butterflies,  they  would 
in  three  or  four  generations  swarm  over  the  whole  country. 
Now  if  a  member  of  one  of  these  persecuted  and  rare  groups 
were  to  assume  a  dress  so  like  that  of  a  well-protected 
species  that  it  continually  deceived  the  practiced  eyes  of  an 
entomologist,  it  would  often  deceive  predaceous  birds  and 
insects,  and  thus  often  escape  destruction.  Mr.  Bates 
may  almost  be  said  to  have  actually  witnessed  the  process 
by  which  the  mimickers  have  come  so  closely  to  resemble 
the  mimicked;  for  he  found  that  some  of  the  forms  of 
Leptalis  which  mimic  so  many  other  butterflies,  varied  in 
an  extreme  degree.  In  one  district  several  varieties  oc¬ 
curred,  and  of  these  one  alone  resembled,  to  a  certain 
extent,  the  common  Ithomia  of  the  same  district.  In 
another  district  there  were  two  or  three  varieties,  one  of 
which  was  much  commoner  than  the  others,  and  this 
closely  mocked  another  form  of  Ithomia.  From  facts  of 
this  nature,  Mr.  Bates  concludes  that  the  Leptalis  first 
varies;  and  when  a  variety  happens  to  resemble  in  some 
degree  any  common  butterfly  inhabiting  the  same  district, 
this  variety,  from  its  resemblance  to  a  flourishing  and  little 
persecuted  kind,  has  a  better  chance  of  escaping  destruc¬ 
tion  from  predaceous  birds  and  insects,  and  is  consequently 
oftener  preserved;  “  the  less  perfect  degrees  of  resemblance 
being  generation  after  generation  eliminated,  and  only  the 
others  left  to  propagate  their  kind.”  So  that  here  we  have 
an  excellent  illustration  of  natural  selection. 

Messrs.  Wallace  and  Trimen  have  likewise  described 


ANALOGICAL  RESEMBLANCES. 


445 


several  equally  striking  cases  of  imitation  in  the  Lepidop- 
tera  of  the  Malay  Archipelago  and  Africa,  and  with  some 
other  insects.  Mr.  Wallace  has  also  detected  one  such  case 
with  birds,  but  we  have  none  with  the  larger  quadrupeds. 
The  much  greater  frequency  of  imitation  with  insects  than 
with  other  animals,  is  probably  the  consequence  of  their 
small  size;  insects  cannot  defend  themselves,  excepting  in¬ 
deed  the  kinds  furnished  with  a  sting,  and  I  have  never 
heard  of  an  instance  of  such  kinds  mocking  other  insects, 
though  they  are  mocked;  insects  cannot  easily  escape  by 
flight  from  the  larger  animals  which  prey  on  them;  there¬ 
fore,  speaking  metaphorically,  they  are  reduced,  like  most 
weak  creatures,  to  trickery  and  dissimulation. 

It  should  be  observed  that  the  process  of  imitation  prob¬ 
ably  never  commenced  between  forms  widely  dissimilar  in 
color.  But,  starting  with  species  already  somewhat  like  each 
other,  the  closest  resemblance,  if  beneficial,  could  readily  be 
gained  by  the  above  means,  and  if  the  imitated  form  was 
subsequently  and  gradually  modified  through  any  agency, 
the  imitating  form  would  be  led  along  the  same  track,  and 
thus  be  altered  to  almost  any  extent,  so  that  it  might  ulti¬ 
mately  assume  an  appearance  or  coloring  wholly  unlike 
that  of  the  other  members  of  the  family  to  w7hich  it  be¬ 
longed.  There  is,  however,  some  difficulty  on  this  head, 
for  it  is  necessary  to  suppose  in  some  cases  that  ancient 
members  belonging  to  several  distinct  groups,  before  they 
had  diverged  to  their  present  extent,  accidentally  resem¬ 
bled  a  member  of  another  and  protected  group  in  a  suffi¬ 
cient  degree  to  afford  some  slight  protection,  this  having 
given  the  basis  for  the  subsequent  acquisition  of  the  most 
perfect  resemblance. 

OK  THE  NATURE  OF  THE  AFFINITIES  CONNECTING 

ORGANIC  BEINGS. 

As  the  modified  descendants  of  dominant  species,  belong¬ 
ing  to  the  larger  genera,  tend  to  inherit  the  advantages 
which  made  the  groups  to  which  they  belong  large  and 
their  parents  dominant,  they  are  almost  sure  to  spread 
widely,  and  to  seize  on  more  and  more  places  in  the 
economy  of  nature.  The  larger  and  more  dominant 
groups  within  each  class  thus  tend  to  go  on  increasing  in 


AFFINITIES  CONNECTING 


446 

size,  and  they  consequently  supplant  many  smaller  and 
feebler  groups.  Thus,  we  can  account  for  the  fact  that 
all  organisms,  recent  and  extinct,  are  included  under  a  few 
great  orders  and  under  still  fewer  classes.  As  showing 
how  few  the  higher  groups  are  in  number,  and  how  widely 
they  are  spread  throughout  the  world,  the  fact  is  striking 
that  the  discovery  of  Australia  has  not  added  an  insect 
belonging  to  a  new  class,  and  that  in  the  vegetable  king¬ 
dom,  as  I  learn  from  Dr.  Hooker,  it  has  added  only  two  or 
three  families  of  small  size. 

In  the  chapter  on  geological  succession  I  attempted  to 
show,  on  the  principle  of  each  group  having  generally 
diverged  much  in  character  during  the  long-continued 
process  of  modification,  how  it  is  that  the  more  ancient 
forms  of  life  often  present  characters  in  some  degree  inter¬ 
mediate  between  existing  groups.  As  some  few  of  the 
old  and  intermediate  forms  have  transmitted  to  the  present 
day  descendants  but  little  modified,  these  constitute  our  so- 
called  osculant  or  aberrant  species.  The  more  aberrant 
any  form  is,  the  greater  must  be  the  number  of  connecting 
forms  which  have  been  exterminated  and  utterly  lost. 
And  we  have  evidence  of  aberrant  groups  having  suffered 
severely  from  extinction,  for  they  are  almost  always  repre¬ 
sented  by  extremely  few  species,  and  such  species  as  do 
occur  are  generally  very  distinct  from  each  other,  which 
again  implies  extinction.  The  genera  Ornithorhynchus 
and  Lepidosiren,  for  example,  would  not  have  been  less 
aberrant  had  each  been  represented  by  a  dozen  species,  in¬ 
stead  of  as  at  present  by  a  single  one,  or  by  two  or  three. 
We  can,  I  think,  account  for  this  fact  only  by  looking  at 
aberrant  groups  as  forms  which  have  been  conquered  by 
more  successful  competitors,  with  a  few  members  still 
preserved  under  unusually  favorable  conditions. 

Mr.  Waterhouse  has  remarked  that  when  a  member 
belonging  to  one  group  of  animals  exhibits  an  affinity  to  a 
quite  distinct  group,  this  affinity  in  most  cases  is  general 
and  not  special;  thus,  according  to  Mr.  Waterhouse,  of  all 
Rodents,  the  bizcacha  is  most  nearly  related  to  Marsupials; 
but  in  the  joints  in  which  it  approaches  this  order,  its 
relations  are  general,  that  is,  not  to  any  one  Marsupial 
species  more  than  to  another.  As  these  points  of  affinity 
are  believed  to  be  real  and  not  merely  adaptive,  they  must 


ORGANIC  BEINGS. 


4-47 


be  due  in  accordance  with  our  view  to  inheritance  from  a 
common  progenitor.  Therefore,  we  must  suppose  either 
that  all  Rodents,  including  the  bizcacha,  branched  off  from 
some  ancient  Marsupial,  which  will  naturally  have  been 
more  or  less  intermediate  in  character  with  respect  to  all 
existing  Marsupials;  or  that  both  Rodents  and  Marsupials 
branched  off  from  a  common  progenitor,  and  that  both 
groups  have  since  undergone  much  modification  in  divergent 
directions.  On  either  view  we  must  suppose  that  the 
bizcacha  has  retained,  by  inheritance,  more  of  the  char¬ 
acters  of  its  ancient  progenitor  than  have  other  Rodents; 
and  therefore  it  will  not  be  specially  related  to  any  one 
existing  Marsupial,  but  indirectly  to  all  or  nearly  all  Mar¬ 
supials,  from  having  partially  retained  the  character  of 
their  common  progenitor,  or  of  some  early  member  of  the 
grou23.  On  the  other  hand,  of  all  Marsupials,  as  Mr. 
Waterhouse  has  remarked,  the  Phascolomys  resembles 
most  nearly,  not  any  one  species,  but  the  general  order  of 
Rodents.  In  this  case,  however,  it  may  be  strongly  sus¬ 
pected  that  the  resemblance  is  only  analogical,  owing  to 
the  Phascolomys  having  become  adapted  to  habits  like 
those  of  a  Rodent.  The  elder  De  Candolle  has  made 
nearly  similar  observations  on  the  general  nature  of  the 
affinities  of  distinct  families  of  plants. 

On  the  principle  of  the  multiplication  and  gradual  diver¬ 
gence  in  character  of  the  species  descended  from  a  com¬ 
mon  progenitor,  together  with  their  retention  by  inherit¬ 
ance  of  some  characters  in  common,  we  can  understand 
the  excessively  complex  and  radiating  affinities  by  which 
all  the  members  of  the  same  family  or  higher  group  are 
connected  together.  For  the  common  progenitor  of  a 
whole  family,  now  broken  up  by  extinction  into  distinct 
groups  and  subgroups,  will  have  transmitted  some  of  its 
characters,  modified  in  various  ways  and  degrees,  to  all  the 
species;  and  they  will  consequently  be  related  to  each 
other  by  circuitous  lines  of  affinity  of  various  lengths  (as 
may  be  seen  in  the  diagram  so  often  referred  to),  mounting 
up  through  many  predecessors.  As  it  is  difficult  to  show 
the  blood  relationship  between  the  numerous  kindred  of 
any  ancient  and  noble  family,  even  by  the  aid  of  a  genea¬ 
logical  tree,  and  almost  impossible  to  do  so  without  this 
aid,  we  can  understand  the  extraordinary  difficulty  which 


448 


AFFINITIES  CONNECTING 


naturalists  have  experienced  in  describing,  without  the  aid 
of  a  diagram,  the  various  affinities  which  they  perceive 
between  the  many  living  and  extinct  members  of  the  same 
great  natural  class. 

Extinction,  as  we  have  seen  in  the  fourth  chapter,  has 
played  an  important  part  in  defining  and  widening  the 
intervals  between  the  several  groups  in  each  class.  We 
mav  thus  account  for  the  distinctness  of  whole  classes  from, 
each  other— for  instance,  of  birds  from  all  other  vertebrate 
animals — by  the  belief  that  many  ancient  forms  of 
life  have  been  utterly  lost,  through  which  the  early  pro¬ 
genitors  of  birds  were  formerly  connected  with  the  early 
progenitors  of  the  other  and  at  that  time  less  differentiated 
vertebrate  classes.  There  has  been  much  less  extinction 
of  the  forms  of  life  which  once  connected  fishes  with 
Batrachians.  There  has  been  still  less  within  some  whole 
classes,  for  instance  the  Crustacea,  for  here  the  most  won¬ 
derfully  diverse  forms  are  still  linked  together  by  a  Iona* 
and  only  partially  broken  chain  of  affinities.  Extinction 
has  only  defined  the  groups:  it  had  by  no  means  made 
them;  for  if  every  form  which  has  ever  lived  on  this  earth 
were  suddenly  to  reappear,  though  it  would  be  quite  im¬ 
possible  to  give  definitions  by  which  each  group  could  be 
distinguished,  still  a  natural  classification,  or  at  least  a 
natural  arrangement,  would  be  possible.  We  shall  see  this 
by  turning  to  the  diagram;  the  letters,  A  to  L,  may  repre¬ 
sent  eleven  Silurian  genera,  some  of  which  have  produced 
large  groups  of  modified  descendants,  with  every  link  in 
each  branch  and  sub-branch  still  alive;  and  the  links  not 
greater  than  those  between  existing  varieties.  In  this  case 
it  would  be  quite  impossible  to  give  definitions  by  which 
the  several  members  of  the  several  groups  could  be  distin¬ 
guished  from  their  more  immediate  parents  and  descend¬ 
ants.  Yet  the  arrangement  in  the  diagram  would  still 
hold  good  and  would  be  natural;  for,  on  the  principle  of 
inheritance,  all  the  forms  descended,  for  instance,  from  A, 
would  have  something  in  common.  In  a  tree  we  can  dis¬ 
tinguish  this  or  that  branch,  though  at  the  actual  fork  the 
two  unite  and  blend  together.  We  could  not,  as  I  have 
said,  define  the  several  groups;  but  we  could  pick  out  types, 
or  forms,  representing  most  of  the  characters  of  each  group, 
whether  large  or  small,  and  thus  give  a  general  idea  of  the 


ORGANIC  BEINGS. 


449 


value  of  the  differences  between  them.  This  is  what  we 
should  be  driven  to,  if  we  were  ever  to  succeed  in  collecting 
all  the  forms  in  any  one  class  which  have  lived  throughout 
all  time  and  space.  Assuredly  we  shall  never  succeed  in 
making  so  perfect  a  collection:  nevertheless,  in  certain 
classes,  we  are  tending  toward  this  end;  and  Milne  Ed¬ 
wards  has  lately  insisted,  in  an  able  paper,  on  the  high 
importance  of  looking  to  types,  whether  or  not  we  can 
separate  and  define  the  groups  to  which  such  types  belong. 

Finally,  we  have  seen  that  natural  selection,  which  fol¬ 
lows  from  the  struggle  for  existence,  and  which  almost 
inevitably  leads  to  extinction  and  divergence  of  character 
in  the  descendants  from  any  one  parent-species,  explains 
that  great  and  universal  feature  in  the  affinities  of  all  or¬ 
ganic  beings,  namely,  their  subordination  in  group  under 
group.  We  use  the  element  of  descent  in  classing  the 
individuals  of  both  sexes  and  of  all  ages  under  one  species, 
although  they  may  have  but  few  characters  in  common;  we 
use  descent  in  classing  acknowledged  varieties,  however 
different  they  may  be  from  their  parents;  and  I  believe 
that  this  element  of  descent  is  the  hidden  bond  of  con¬ 
nection  which  naturalists  have  sought  under  the  term  of 
the  Natural  System.  On  this  idea  of  the  natural  system 
being,  in  so  far  as  it  has  been  perfected,  genealogical  in  its 
arrangement,  with  the  grades  of  difference  expressed  by 
the  terms  genera,  families,  orders,  etc.,  we  can  under¬ 
stand  the  rules  which  we  are  compelled  to  follow  in 
our  classification.  We  can  understand  why  we  value 
certain  resemblances  far  more  than  others ;  why  we 
use  rudimentary  and  useless  organs,  or  others  of  trifling 
physiological  importance;  why,  in  finding  the  relations 
between  one  group  and  another,  we  summarily  reject  ana¬ 
logical  or  adaptive  characters,  and  yet  use  these  same  char¬ 
acters  within  the  limits  of  the  same  group.  We  can 
clearly  see  how  it  is  that  all  living  and  extinct  forms  can 
be  grouped  together  within  a  few  great  classes;  and  how 
the  several  members  of  each  class  are  connected  together 
by  the  most  complex  and  radiating  lines  of  affinities.  We 
shall  never,  probably,  disentangle  the  inextricable  web  of 
the  affinities  between  the  members  of  any  one  class;  but 
when  we  have  a  distinct  object  in  view,  and  do  not  look 
to  some  unknown  plan  of  creation,  we  may  hope  to  make 
sure  but  slow  progress*  — 


450 


MORPHOLOGY. 


Professor  Hackel  in  liis  “Generelle  Morphologic”  and 
in  other  works,  has  recently  brought  his  great  knowledge 
and  abilities  to  bear  on  what  he  calls  phylogeny,  or  the 
lines  of  descent  of  all  organic  beings.  In  drawing  up  the 
several  series  he  trusts  chiefly  to  embryological  characters, 
but  receives  aid  from  homologous  and  rudimentary  organs, 
as  well  as  from  the  successive  periods  at  which  the  various 
forms  of  life  are  believed  to  have  first  appeared  in  our 
geological  formations.  He  has  thus  boldly  made  a  great 
beginning,  and  shows  us  how  classification  will  in  the 

future  be  treated. 

* 

MORPHOLOGY. 

We  have  seen  that  the  members  of  the  same  class,  in¬ 
dependently  of  their  habits  of  life,  resemble  each  other  in 
the  generafplan  of  their  organization.  This  resemblance 
is  often  expressed  by  the  term  “  unity  of  type;”  or  by  say¬ 
ing  that  the  several  parts  and  organs  in  the  different 
species  of  the  class  are  homologous.  The  whole  subject  is 
included  under  the  general  term  of  Morphology.  This  is 
one  of  the  most  interesting  departments  of  natural  history, 
and  may  almost  be  said  to  be  its  very  soul.  What  can  be 
more  curious  than  that  the  hand  of  a  man,  formed  for 
giasping,  that  of  a  mole  for  digging,  the  leg  of  the  horse, 
the  paddle  of  the  porpoise,  and  the  wing  of  the  bat,  should 
all  be  constructed  on  the  same  pattern,  and  should  include 
similar  bones,  in  the  same  relative  positions?  How  curious 
it  is,  to  give  a  subordinate  though  striking  instance,  that 
the  hind  feet  of  the  kangaroo,  which  are  so  well  fitted  for 
bounding  over  the  open  plains — those  of  the  climbing,  leaf¬ 
eating  koala,  equally  well  fitted  for  grasping  the  branches 
of  trees — those  of  the  ground-dwelling,  insect  or  poot-eat- 
ing,  bandicoots — and  those  of  some  other  Australian  mar¬ 
supials — should  all  be  constructed  on  the  same  extraor¬ 
dinary  type,  namely  with  the  bones  of  the  second  and 
third  digits  extremely  slender  and  enveloped  within  the 
same  skin,  so  that  they  appear  like  a  single  toe  furnished 
with  two  claws.  Notwithstanding  this  similarity  of  pat¬ 
tern,  it  is  obvious  that  the  hind  feet  of  these  several 
animals  are  used  for  as  widely  different  purposes  as  it  is 
possible  to  conceive.  The  case  is  rendered  all  the  more 


MORPHOLOGY. 


451 


striking  by  the  American  opossums,  which  follow  nearly 
the  same  habits  of  life  as  some  of  their  Australian  relatives, 
having  feet  constructed  on  the  o  .‘dinary  plan.  Professor 
Flower,  from  whom  these  statements  are  taken,  remarks 
in  conclusion:  “We  may  call  this  conformity  to  type, 
without  getting  much  nearer  to  an  explanation  of  the 
phenomenon;”  and  he  then  adds  “but  is  it  not  powerfully 
suggestive  of  true  relationship,  of  inheritance  from  a 
common  ancestor?” 

Geoffroy  St.  Hilaire  has  strongly  insisted  on  the  high 
importance  of  relative  position  or  connection  in  homolo¬ 
gous  parts;  they  may  differ  to  almost  any  extent  in  form 
and  size,  and  yet  remain  connected  together  in  the 
same  invariable  order.  We  never  find,  for  instance,  the 
bones  of  the  arm  and  forearm,  or  of  the  thigh  and  leg, 
transposed.  Hence,  the  same  names  can  be  given  to  the 
homologous  bones  in  widely  different  animals.  We  see  the 
same  great  law  in  the  construction  of  the  mouths  of  insects: 
what  can  be  more  different  than  the  immensely  long 
spiral  proboscis  of  a  sphinx-moth,  the  curious  folded  one 
of  a  bee  or  bug,  and  the  great  jaws  of  a  beetle?  Yet 
all  these  organs,  serving  for  such  widely  different  purposes, 
are  formed  by  infinitely  numerous  modifications  of  an  upper 
lip,  mandibles,  and  two  pairs  of  maxillae.  The  same  law 
governs  the  construction  of  the  mouths  and  limbs  of 
crustaceans.  So  it  is  with  the  flowers  of  plants. 

Nothing  can  be  more  hopeless  than  to  attempt  to  ex¬ 
plain  this  similarity  of  pattern  in  members  of  the  same 
class,  by  utility  or  by  the  doctrine  of  final  causes.  The 
hopelessness  of  the  attempt  has  been  expressly  admitted  by 
Owen  in  his  most  interesting  work  on  the  “  Nature  of 
Limbs.”  On  the  ordinary  view  of  the  independent  creation 
of  each  being,  we  can  only  say  that  so  it  is;  that  it  has 
pleased  the  Creator  to  construct  all  the  animals  and  plants 
in  each  gretff  class  on  a  uniform  plan;  but  this  is  not  a 
scientific  explanation. 

The  explanation  is  to  a  large  extent  simple,  on  the  theory 
of  the  selection  of  successive  slight  modifications,  each 
being  profitabxo  in  some  way  to  the  modified  form,  but 
often  affecting  by  correlation  other  parts  of  the  organiza¬ 
tion.  In  changes  of  this  nature,  there  will  be  little  or  no 
tendency  to  alter  the  original  pattern,  or  to  transpose  the 


452 


MORPr^LOG  r. 


parts.  The  bones  of  a  limb  might  be  shortened  and  flat¬ 
tened  to  any  extent,  becoming  at  tjie  same  time  enveloped 
in  thick  membrane,  so  as  to  serve  as  a  fin;  or  a  webbed 
hand  might  have  all  its  bones,  or  certain  bones,  lengthened 
to  any  extent,  with  the  membrane  connecting  them 
increased,  so  as  to  serve  as  a  wing;  yet  all  these  modifica¬ 
tions  would  not  tend  to  alter  the  framework  of  the  bones 
or  the  relative  connection  of  the  parts.  If  we  suppose 
that  an  early  progenitor — the  archetype,  as  it  may  be 
called — of  all  mammals,  birds  and  reptiles,  had  its  limbs 
constructed  on  the  existing  general  pattern,  for  whatever 
purpose  they  served,  we  can  at  once  perceive  the  plain 
signification  of  the  homologous  construction  of  the  limbs 
throughout  the  class.  So  with  the  mouths  of  insects,  we 
have  only  to  suppose  that  their  common  progenitor  had  an 
upper  lip,  mandibles,  and  two  pairs  of  maxillae,  these  parts 
being  perhaps  very  simple  in  form;  and  then  natural  selec¬ 
tion  will  account  for  the  definite  diversity  in  the  structure 
and  functions  of  the  mouths  of  insects.  Nevertheless,  it  is 
conceivable  that  the  general  pattern  of  an  organ  might 
become  so  much  obscured  as  to  be  finally  lost,  by  the 
reduction  and  ultimately  by  the  complete  abortion  of  cer¬ 
tain  parts,  by  the  fusion  of  other  parts,  and  by  the  doubling 
or  multiplication  of  others,  variations  which  we  know  to  be 
within  the  limits  of  possibility.  In  the  paddles  of  the 
gigantic  extinct  ,:ea-lizards,  and  in  the  mouths  of  certain 
suctorial  crustaceans,  the  general  pattern  seems  thus  to 
have  become  partially  obscured. 

There  is  another  and  equally  curious  branch  of  our  sub¬ 
ject;  namely,  serial  homologies,  or  the  comparison  of  the 
different  parts  or  organs  in  the  same  individual,  and  not 
of  the  same  parts  or  organs  in  different  members  of  the 
same  class.  Most  physiologists  believe  that  the  bones  of 
the  skull  are  homologous — that  is,  correspond  in  number 
and  in  relative  connection — with  the  elemental  parts  of  a 
certain  number  of  vertebras.  The  anterior  and  posterior 
limbs  in  all  the  higher  vertebrate  classes  are  plainly  homo¬ 
logous.  So  it  is  with  the  wonderfully  complex  jaws  and 
legs  of  crustaceans.  It  is  familiar  to  almost  every  one, 
that  in  a  flower  the  relative  position  of  the  sepals,  petals, 
stamens  and  pistils,  as  well  as  their  intimate  structure,  are 
intelligible  on  the  view  that  they  consist  of  metamorphosed 


MORPHOLOGY. 


453 

]«IY0S,  arranged  in  a  spire.  In  monstrous  plants,  we  often 
get  direct  evidence  of  the  possibility  of  one  organ  being 
transformed  into  another;  and  we  can  actually  see,  during 
the  early  or  embryonic  stages  of  development  in  flowers,  as 
well  as  in  crustaceans  and  many  other  animals,  that  organs 
which  when  mature  become  extremely  different  are  at  first 
exactly  alike. 

How  inexplicable  are  the  cases  of  serial  homologies  on 
the  ordinary  view  of  creation!  Why  should  the  brain  be 
inclosed  in  a  box  composed  of  such  numerous  and  such  ex¬ 
traordinarily  shaped  pieces  of  bone,  apparently  represent¬ 
ing  vertebrae?  As  Owen  has  remarked,  the  benefit  derived 
from  the  yielding  of  the  separate  pieces  in  the  act  of  par¬ 
turition  by  mammals,  will  by  no  means  explain  the  same 
construction  in  the  skulls  of  birds  and  reptiles.  Why 
should  similar  bones  have  been  created  to  form  the  wing 
and  the  leg  of  a  bat,  used  as  they  are  for  such  totally  differ¬ 
ent  purposes,  namely,  flying  and  walking?  Why  should 
one  crustacean,  which  has  an  extremely  complex  mouth 
formed  of  many  parts,  consequently  always  have  fewer 
legs;  or  conversely,  those  with  many  legs  have  simpler 
mouths?  Why  should  the  sepals,  petals,  stamens  and 
pistils,  in  each  flower,  though  fitted  for  such  distinct  pur¬ 
poses,  be  all  constructed  on  the  same  pattern? 

On  the  theory  of  natural  selection,  we  can,  to  a  certain 
extent,  answer  these  questions.  We  need  not  here  con¬ 
sider  how  the  bodies  of  some  animals  first  became  divided 
into  a  series  of  segments,  or  how  they  became  divided  into 
right  and  left  sides,  with  corresponding  organs,  for  such 
questions  are  almost  beyond  investigation.  It  is,  however, 
probable  that  some  serial  structures  are  the  result  of  cells 
multiplying  by  division,  entailing  the  multiplication  of  the 
parts  developed  from  such  cells.  It  must  suffice  for  our 
purpose  to  bear  in  mind  that  an  indefinite  repetition  of  the 
same  part  or  organ  is  the  common  characteristic,  as  Owen 
has  remarked,  of  all  low  or  little  specialized  forms;  there¬ 
fore  the  unknown  progenitor  of  the  Yertebrata  probably 
possessed  many  vertebrae;  the  unknown  progenitor  of  the 
Articulata,  many  segments;  and  the  unknown  progenitor 
of  flowering  plants,  many  leaves  arranged  in  one  or  more 
spires.  We  have  also  formerly  seen  that  parts  many  times 
repeated  are  eminently  liable  to  vary,  not  only  in  number. 


454 


MORPHOLOGY. 


but  in  form.  Consequently  sucli  parts,  being  already  pres¬ 
ent  in  considerable  numbers,  and  being  highly  variable, 
would  naturally  afford  the  materials  for  adaptation  to  the 
most  different  purposes;  yet  they  would  generally  retain, 
through  the  force  of  inheritance,  plain  traces  of  their  orig¬ 
inal  or  fundamental  resemblance.  They  would  retain  this 
resemblance  all  the  more,  as  the  variations,  which  afforded 
the  basis  for  their  subsequent  modification  through  natural 
selection,  would  tend  from  the  first  to  be  similar;  tlm  parts 
being  at  an  early  stage  of  growth  alike,  and  being  subjected 
to  nearly  the  same  conditions.  Such  parts,  whether  more 
or  less  modified,  unless  their  common  origin  became  wholly 
obscured,  would  be  serially  homologous. 

In  the  great  class  of  molluscs,  though  the  parts  in  dis¬ 
tinct  species  can  be  shown  to  be  homologous,  only  a  few 
serial  homologies,  such  as  the  valves  of  Chitons,  can  be 
indicated;  that  is,  we  are  seldom  enabled  to  say  that  one 
part  is  homologous  with  another  part  in  the  same  indi¬ 
vidual.  And  we  can  understand  this  fact;  for  in  molluscs, 
even  in  the  lowest  members  of  the  class,  we  do  not  find 
nearly  so  much  indefinite  repetition  of  any  one  part  as  we 
find  in  the  other  great  classes  of  the  animal  and  vegetable 
kingdoms. 

But  morphology  is  a  much  more  complex  subject  than 
it  at  first  appears,  as  has  lately  been  well  shown  in 
a  remarkable  paper  by  Mr.  E.  Ray  Lankester,  who  has 
drawn  an  important  distinction  between  certain  classes 
of  cases  which  have  all  been  equally  ranked  by  naturalists 
as  homologous.  He  proposes  to  call  the  structures  which 
resemble  each  other  in  distinct  animals,  owing  to  their  de¬ 
scent  from  a  common  progenitor  with  subsequent  modifica¬ 
tion,  homogenous ;  and  the  resemblances  which  cannot  thus 
be  accounted  for,  he  proposes  to  call  homoplastic.  For 
instance,  he  believes  that  the  hearts  of  birds  and  mammals 
are  as  a  whole  homogenous — that  is,  have  been  derived 
from  a  common  progenitor;  but  that  the  four  cavities  of  the 
heart  in  the  two  classes  are  homoplastic — that  is,  have  been 
independently  developed.  Mr.  Lankester  also  adduces  the 
close  resemblance  of  the  parts  on  the  right  and  left  sides  of 
the  body,  and  in  the  successive  segments  of  the  same  indi¬ 
vidual  animal;  and  here  we  have  parts  commonly  called 
homologous  which  bear  no  relation  to  the  descent  of  dis- 


DEVELOPMENT  AND  EMBRYOLOGY. 


455 


tinct  species  from  a  common  progenitor.  Homoplastic 
structures  are  the  same  with  those  which  I  have  classed, 
though  in  a  very  imperfect  manner,  as  analogous  modifica¬ 
tions  or  resemblances.  Their  formation  may  be  attributed 
in  part  to  distinct  organisms,  or  to  distinct  parts  of  the 
same  organism,  having  varied  in  an  analogous  manner; 
and  in  part  to  similar  modifications,  having  been  preserved 
for  the  same  general  purpose  or  function,  of  which  many 
instances  have  been  given. 

Naturalists  frequently  speak  of  the  skull  as  formed  of 
metamorphosed  vertebrae;  the  jaws  of  crabs  as  metamor¬ 
phosed  legs;  the  stamens  and  pistils  in  flowers  as  metamor¬ 
phosed  leaves;  but  it  would  in  most  cases  be  more  correct, 
as  Professor  Huxley  has  remarked,  to  speak  of  both  skull 
and  vertebrae,  jaws  and  legs,  etc.,  as  having  been  metamor¬ 
phosed,  not  one  from  the  other,  as  they  now  exist,  but 
from  some  common  and  simpler  element.  Most  natural¬ 
ists,  however,  use  such  language  only  in  a  metaphorical 
sense;  they  are  far  from  meaning  that  during  a  long  course 
of  descent,  primordial  organs  of  any  kind — vertebrae  in  the 
one  case  and  legs  in  the  other — -have  actually  been  con¬ 
verted  into  skulls  or  jaws.  Yet  so  strong  is  the  appearance 
of  this  having  occurred  that  naturalists  can  hardly  avoid 
employing  language  having  this  plain  signification.  Ac¬ 
cording  to  the  views  here  maintained,  such  language  may 
be  used  literally;  and  the  wonderful  fact  of  the  jaws,  for 
instance,  of  a  crab  retaining  numerous  characters,  which 
they  probably  would  have  retained  through  inheritance,  if 
they  had  really  been  metamorphosed  from  true  though  ex¬ 
tremely  simple  legs,  is  in  part  explained. 

DEVELOPMENT  AND  EMBRYOLOGY. 

This  is  one  of  the  most  important  subjects  in  the  whole 
round  of  natural  history.  The  metamorphoses  of  insects, 
with  which  every  one  is  familiar,  are  generally  effected 
abruptly  by  a  few  stages;  but  the  transformations  are  in 
reality  numerous  and  gradual,  though  concealed.  A  cer¬ 
tain  ephemerous  insect  (Chloeon)  during  its  development, 
moults,  as  shown  by  Sir  J.  Lubbock,  above  twenty  times, 
and  each  time  undergoes  a  certain  amount  of  change;  and 
in  this  case  we  see  the  act  of  metamorphosis  performed  in 


456  DEVELOPMENT  AND  EMBR  TO  LOO  T. 

a  primary  and  gradual  manner.  Many  insects,  and  espec¬ 
ially  certain  crustaceans,  show  us  what  wonderful  changes 
of  structure  can  be  effected  during  development.  Such 
changes,  however,  reach  their  acme  in  the  so-called  alternate 
generations  of  some  of  the  lower  animals.  It  is,  for  instance 
an  astonishing  fact  that  a  delicate  branching  coralline,  stud¬ 
ded  with  polypi,  and  attached  to  a  submarine  rock,  should 
produce,  first  by  budding  and  then  by  transverse  division 
a  host  of  huge  floating  jelly-fishes;  and  that  these  should 
produce  eggs,  from  which  are  hatched  swimming  animal¬ 
cules,  which  attach  themselves  to  rocks  and  become  devel¬ 
oped  into  branching  corallines;  and  so  on  in  an  endless 
cycle.  The  belief  in  the  essential  identity  of  the  process 
of  alternate  generation  and  of  ordinary  metamorphosis  has 
been  greatly  strengthened  by  Wagner's  discovery  of  the 
larva  or  maggot  of  a  fly,  namely  the  Cecidomyia,  produc¬ 
ing  asexually  other  larvae,  and  these  others,  which  finally 
aie  developed  into  mature  males  and  females,  propagating 
their  kind  in  the  ordinary  manner  by  eggs. 

It  may  be  worth  notice  that  when  Wagner's  remarkable 
discovery  was  first  announced,  I  was  asked  how  was  it  pos¬ 
sible  to  account  for  the  larvae  of  this  fly  having  acquired 
the  power  of  asexual  reproduction.  As  long  as  the  case 
remained  unique  no  answer  could  be  given.  But  already 
Cxi  ini m  has  shown  that  another  fly,  a  Ohironomus,  repro- 
duces  itself  in  nearly  the  same  manner,  and  he  believes 
that  this  occurs  frequently  in  the  order.  It  is  the  pupa 
and  not  the  larva,  of  the  Ohironomus  which  has  this 
power;  and  Grimm  further  shows  that  this  case,  to  a  cer¬ 
tain  extent,  “unites  that  of  the  Cecidomyia  with  the 
pai  thenogenesis  of  the  Coccidas;"  the  term  parthenogen- 
esis  implying  that  the  mature  females  of  the  Coccid®  are 
capable  of  producing  fertile  eggs  without  the  concourse  of 
the  male.  Certain  animals  belonging  to  several  classes  are 
now  Known  to  have  the  power  of  ordinary  reproduction  at 
an  unusually  early  age;  and  we  have  only  to  accelerate 
parthenogenetic  reproduction  by  gradual  steps  to  an  earlier 
ana  earlier  age— Ohironomus  showing  us  an  almost  exactly 
intermediate  stage,  viz.,  that  of  the  pupa — and  we  can 
perhaps  account  for  the  marvelous  case  of  the  Cecidomyia. 

It  has  already  been  stated  that  various  parts  in  the  same 
individual,  which  are  exactly  alike  during  an  early  embry- 


1)E  VELOPMENT  AND  EMBlt  TO  LOO  Y.  457 

onic  period,  become  widely  different  and  serve  for  widely 
different  purposes  in  the  adult  state.  So  again  it  has 
been  shown  that  generally  the  embryos  of  the  most 
distinct  species  belonging  to  the  same  class  are  closely 
similar,  but  become,  when  fully  developed,  widely 
dissimilar.  A  better  proof  of  this  latter  fact  can  not  be 
given  than  the  statement  by  Von  Baer  that  “  the  embryos 
of  mammalia,  of  birds,  lizards  and  snakes,  probably  also 
of  chelonia,  are  in  the  earliest  states  exceedingly  like  one 
another,  both  as  a  whole  and  in  the  mode  of  development 
of  their  parts;  so  much  so,  in  fact,  that  we  can  often  dis¬ 
tinguish  the  embryos  only  by  their  size.  In  my  possession 
are  two  little  embryos  in  spirit,  whose  names  I  have 
omitted  to  attach,  —  1  at  present  I  am  quite  unable  to  say 
to  what  class  they  belong.  They*  may  be  lizards  or  small 
birds,  or  very  ycuii"  mammalia,  .:o  complete  is  the  similar¬ 
ity  in  the  mode  of  formation  of  the  head  and  trunk  in  these 
animals.  The  extremities,  however,  are  still  absent  in 
these  embryos.  But  even  if  they  had  existed  in  the  earliest 
stage  of  their  development  we  should  learn  nothing,  for 
the  feet  of  lizards  and  mammals,  the  wings  and  feet  of 
birds,  no  less  than  the  hands  and  feet  of  man,  all  arise 
from  the  same  fundamental  form.”  The  larvae  of  most 
crustaceans,  at  corresponding  stages  of  development, 
closely  resemble  each  other,  however  different  the  adults 
may  become;  and  so  it  is  with  very  many  other  animals. 
A  trace  of  the  law  of  embryonic  resemblance  occasionally 
lasts  till  a  rather  late  age:  thus  birds  of  the  same  genus, 
and  of  allied  genera,  often  resemble  each  other  in  their 
immature  plumage;  as  we  see  in  the  spotted  feathers  in  the 
young  of  the  thrush  group.  In  the  cat  tribe,  most  of  the 
species  when  adult  are  striped  or  spotted  in  lines;  and 
stripes  or  spots  can  be  plainly  distinguished  in  the  whelp 
of  the  lion  and  the  puma.  We  occasionally,  though  rarely, 
see  something  of  the  same  kind  in  plants;  thus  the  first 
leaves  of  the  ulex  or  furze,,  and  the  first  leaves  of  the 
phyllodineous  acacias,  are  pinnate  or  divided  like  the 
ordinary  leaves  of  the  leguminosse. 

I. he  points  of  structure,  in  which  the  embryos  of  widely 
different  animals  within  the  same  class  resemble  each  other, 
often  have  no  direct  relation  to  their  conditions  of  exist¬ 
ence.  We  can  not,  for  instance,  suppose  that  in  the  era* 


m 


DEVELOPMENT  AND  EMBRYOLOGY. 


bryos  of  the  vertebrata  the  peculiar  loop-like  courses  of  th& 
arteries  near  the  branchial  slits  are  related  to  similar  con¬ 
ditions — in  the  young  mammal  which  is  nourished  in  the 
womb  of  its  mother,  in  the  egg  of  the  bird  which  is  hatched 
in  a  nest,  and  in  the  spawn  of  a  frog  under  water.  We 
have  no  more  reason  to  believe  in  such  a  relation  than  we 
have  to  believe  that  the  similar  bones  in  the  hand  of  a 
man,  wing  of  a  bat,  and  fin  of  porpoise,  are  related  to 
similar  conditions  of  life.  No  one  supposes  that  the  stripes 
on  the  whelp  of  a  lion,  or  the  spots  on  the  young  black¬ 
bird,  are  of  any  use  to  these  animals. 

The  case,  however,  is  different  when  an  animal,  during 
any  part  of  its  embryonic  career,  is  active,  and  has  to  pro¬ 
vide  for  itself.  The  period  of  activity  may  come  on 
earlier  or  later  in  life;  but  whenever  it  comes  on,  the 
adaptation  of  the  larva  to  its  conditions  of  life  is  just  as  per¬ 
fect  and  as  beautiful  as  in  the  adult  animal.  In  how  im¬ 
portant  a  manner  this  has  acted,  has  recently  been 
well  shown  by  Sir  J.  Lubbock  in  his  remarks  on  the 
close  similarity  of  the  larv®  of  some  insects  belonging 
to  very  different  orders,  and  on  the  dissimilarity  of  the 
larvae  of  other  insects  within  the  same  order,  according 
to  their  habits  of  life.  Owing  to  such  adaptations  the 
similarity  of  the  larvae  of  allied  animals  is  sometimes 
greatly  obscured;  especially  when  there  is  a  division  of 
labor  during  the  different  stages  of  development,  as 
when  the  same  larva  has  during  one  stage  to  search  for 
food,  and  during  another  stage  has  to  search  for  a  place  of 
attachment.  Cases  can  even  be  given  of  the  larvse  of  allied 
species,  or  groups  of  species,  differing  more  from  each 
other  than  do  the  adults.  In  most  cases,  however,  the 
larvae,  though  active,  still  obey,  more  or  less  closely,  the 
law  of  common  embryonic  resemblance.  Cirripedes  afford 
a  good  instance  of  this;  even  the  illustrious  Cuvier  did  not 
perceive  that  a  barnacle  was  a  crustacean:  but  a  glance  at 
the  larva  shows  this  in  an  unmistakable  manner.  So  again 
the  two  main  divisions  of  cirripedes,  the  pedunculated  and 
sessile,  though  differing  widely  in  external  appearance, 
have  larvag  in  all  their  stages  barely  distinguishable. 

The  embryo  in  the  course  of  development  generally  rises 
in  organization.  I  use  this  expression,  though  I  am  aware 
that  it  is  hardly  possible  to  define  clearly  what  is  meant  by 


Development  and  embryology.  459 

organization  being  higher  or  lower.  But  no  one  probably 
will  dispute  that  the  butterfly  is  higher  than  the  cater¬ 
pillar.  .  In  some  cases,  however,  the  mature  animal  must 
De  considered  as  lower  in  the  scale  than  the  larva,  as  with 
certain  parasitic  crustaceans.  To  refer  once  again  to  cirri- 
pedes:  the  larvae  in  the  first  stage  have  three  pairs  of  loco¬ 
motive  organs,  a  simple  single  eye,  and  a  probosciformed 
mouth,,  with  which  they  feed  largely,  for  they  increase 
much  in  size.  In  the  second  stage,  answering  to  the 
chiysalis  stage  of  butterflies,  they  have  six  pairs  of  beauti¬ 
fully  constructed  natatory  legs,  a  pair  of  magnificent  com¬ 
pound  eyes,  and  extremely  complex  antenna;;  but  they 
nave  a  closed  and  imperfect  mouth,  and  cannot  feed:  their 
function  at  this  stage  is,  to  search  out  by  their  well-devel¬ 
oped  organs  of  sense,  and  to  reach  by  their  active  powers 
of  swimming,  a  proper  place  on  which  to  become  attached 
and  to  undergo  their  final  metamorphosis.  When  this  is 
completed  they  are  fixed  for  life:  their  legs  are  now  con¬ 
verted  into  prehensile  organs;  they  again  obtain  a  well- 
constructed  mouth;  but  they  have  no  antennae,  and  their 
two  eyes  are  now  reconverted  into  a  minute,  single,  simple 
eye-spot.  I11  this,  last  and  complete  state,  cirripedes  may 
be  considered  as  either  more  highly  or  more  lowly  organized 
than  they  were  in  the  larval  condition.  But  in  some  genera 
the  laryas  become  developed  into  hermaphodites  having 
the  ordinary  structure,  and  into  what  I  have  called  com- 
plemental  males;  and  in  the  latter  the  development  has 
assuredly  been  retrograde,  for  the  male  is  a  mere  sack, 
which  lives  for  a  short  time  and  is  destitute  of  mouth, 
stomach,  and  every  other  organ  of  importance,  excepting 
those  for  reproduction. 

We  are  so  much  accustomed  to  see  a  difference  in  struc¬ 
ture  between  the  embryo  and  the  adult,  that  we  are  tempted 
to  look  at  this  difference  as  in  some  necessary  manner 
contingent  on  growth.  But  there  is  no  reason  why,  for 
instance,  the  wing  of  a  bat,  or  the  fin  of  a  porpoise,  should 
not  have  been  sketched  out  with  all  their  parts  in  proper 
proportion,  as  soon  as  any  part  became  visible.  In  some 
whole  groups  of  animals  and  in  certain  members  of  other 
groups  this  is  the  case,  and  the  embryo  does  not  at  any 
period  differ  widely  from  the  adult:  thus  Owen  has  re¬ 
marked  in  regard  to  cuttle-fish,  “  there  is  no  metamor- 


460 


DEVELOPMENT  AND  EMBRYOLOGY. 


phosis;  the  cephalopodic  character  is  manifested  long  be¬ 
fore  the  parts  of  the  embryo  are  completed."  Land-shells 
and  fresh-water  crustaceans  are  born  having  their  proper 
forms,  while  the  marine  members  of  the  same  two  great 
classes  pass  through  considerable  and  often  great  changes 
during  their  development.  Spiders,  again,  barely  undergo 
any  metamorphosis.  The  larvae  of  most  insects  pass  through 
a  worm-like  stage,  whether  they  are  active  and  adapted  to 
diversified  habits,  or  are  inactive  from  being  placed  in  the 
midst  of  proper  nutriment,  or  from  being  fed  by  their 
parents;  but  in  some  few  cases,  as  in  that  of  Aphis,  if  we 
look  to  the  admirable  drawings  of  the  development  of  this 
insect,  by  Professor  Huxley,  we  see  hardly  any  trace  of  tiie 
vermiform  stage. 

Sometimes  it  is  only  the  earlier  developmental  stages 
which  fail.  Thus,  Fritz  Muller  has  made  the  remarkable 
discovery  that  certain  shrimp-like  crustaceans  (allied  to 
Penceus)  first  appear  under  the  simple  nauplius-form,  and 
after  passing  through  two  or  more  zoea-stages,  and  then 
through  the  mysis-stage,  finally  acquire  their  mature 
structure:  now  in  the  whole  great  malacostracan  order,  to 
which  these  crustaceans  belong,  no  other  member  is  as  yet 
known  to  be  first  developed  under  the  nauplius-form, 
though  many  appear  as  zoeas;  nevertheless  Muller  assigns 
reasons  for  his  belief,  that  if  there  had  been  no  suppression 
of  development,  all  these  crustaceans  would  have  appeared 
as  nauplii. 

How,  then,  can  we  explain  these  several  facts  in  embry¬ 
ology — namely,  the  very  general,  though  not  universal, 
difference  in  structure  between  the  embryo  and  the  adult; 
the  various  parts  in  the  same  individual  embryo,  which 
ultimately  become  very  unlike,  and  serve  for  diverse  pur¬ 
poses,  being  at  an  early  period  of  growth  alike;  the  com¬ 
mon,  but  not  invariable,  resemblance  between  the  embryos 
or  larvae  of  the  most  distinct  species  in  the  same  class;  the 
embryo  often  retaining,  while  within  the  egg  or  womb, 
structures  which  are  of  no  service  to  it,  either  at  that  or  at 
a  later  period  of  life;  on  the  other  hand,  larvae  which  have 
to  provide  for  their  own  wants,  being  perfectly  adapted  to 
the  surrounding  conditions;  and  lastly,  the  fact  of  certain 
larvae  standing  higher  in  the  scale  of  organization  than  the 
mature  animal  into  which  they  are  developed?  I  believe 
that  all  these  facts  can  be_explained  as  follows. 


DEVELOPMENT  AND  EMBRYOLOGY. 


461 


It  is  commonly  assumed,  perhaps  from  monstrosities 
affecting  the  embryo  at  a  very  early  period,  that  slight 
variations  or  individual  differences  necessarily  appear  at  an 
equally  early  period.  We  have  little  evidence  on  this 
head,  but  what  we  have  certainly  points  the  other  wav;  for 
it  is  notorious  that  breeders  of  cattle,  horses  and  various 
fancy  animals,  can  not  positively  tell,  until  some  time  after 
birth,  what  will  be  the  merits  and  demerits  of  their  young 
animals.  We  see  this  plainly  in  our  own  children;  we 
can  not  tell  whether  a  child  will  be  tall  or  short,  or  what 
its  precise  features  will  be.  The  question  is  not,  at  what 
period  of  life  each  variation  may  have  been  caused,  but  at 
what  period  the  effects  are  displayed.  The  cause  may  have 
acted,  and  I  believe  often  has  acted,  on  one  or  both  par¬ 
ents  before  the  act  of  generation.  It  deserves  notice  that 
it  is  of  no  importance  to  a  very  young  animal,  as  long  as  it 
remains  in  its  mothers  womb  or  in  the  egsr,  or  as  long  as 
it  is  nourished  and  protected  by  its  parent,  whether  most 
of  its  characters  are  acquired  a  little  earlier  or  later  in  life. 
It  would  not  signify,  for  instance,  to  a  bird  which  obtained 
its .  food  by  having  a  much-curved  beak  whether  or  not 
while  young  it  possessed  a  beak  of  this  shape,  as  long  as  it 
was  fed  by  its  parents. 

I  have  stated  in  the  first  chapter,  that  at  whatever  age  a 
\aiiation  first  appears  in  the  parent,  it  tends  to  reappear 
at  a  corresponding  age  in  the  offspring.  Certain  vari¬ 
ations  can  only  appear  at  corresponding  ages;  for  instance, 
peculiarities  in  the  caterpillar,  cocoon,  or  imago  states  of 
the  silk-moth;  or,  again,  in  the  full-grown  horns  of  cattle. 
But  variations  which,  for  all  that  we  can  see  might  have 
first  appeared  either  earlier  or  later  in  life,  likewise  tend  to 
reappear  at  a  corresponding  age  in  the  offspring  and 
parent.  I  am  far  from  meaning  that  this  is  invariably  the 
case,  and  I  could  give  several  exceptional  cases  of  varia¬ 
tions  (taking  the  word  in  the  largest  sense)  which 
have  supervened  at  an  earlier  age  in  the  child  than  in  the 
parent. 

These  two  principles,  namely,  that  slight  variations  gen¬ 
erally  appear  at  a  not  very  early  period  of  life,  and  are  in¬ 
herited  at  a  corresponding  not  early  period,  explain,  as  I 
believe,  all  the  above  specified  leading  facts  in  embryology. 
But  first  let  us  look  to  a  few  analogous  cases  in  our  domes- 


462 


DEVELOPMENT  aN O  EMBRYOLOGY. 


tic  varieties.  Some  authors  who  have  written  on  dogs 
maintain  that  the  greyhound  and  bull-dog,  though  so  dif¬ 
ferent,  are  really  closely  allied  varieties,  descended  from 
the  same  wild  stock,  hence  I  was  curious  to  see  how  far 
their  puppies  differed  from  each  other.  I  was  told  by 
breeders  that  they  differed  just  as  much  as  their  parents, 
and  this,  judging  by  the  eye,  seemed  almost  to  be  the  case; 
but  on  actually  measuring  the  old  dogs  and  their  six-days- 
old  puppies,  I  found  that  the  puppies  had  not  acquired 
nearly  their  full  amount  of  proportional  difference.  So, 
again,  I  was  told  that  the  foals  of  cart  and  race  horses — • 
breeds  which  have  been  almost  wholly  formed  by  selection 
under  domestication — differed  as  much  as  the  full-grown 
animals;  but  having  had  careful  measurements  made  of 
the  dams  and  of  three-days-old  colts  of  race  and  heavy 
cart-horses,  I  find  that  this  is  by  no  means  the  case. 

As  we  have  conclusive  evidence  that  the  breeds  of  the 
pigeon  are  descended  from  a  single  wild  species,  I  com¬ 
pared  the  young  within  twelve  hours  after  being  hatched. 
I  carefully  measured  the  proportions  (but  will  not  here 
give  the  details)  of  the  beak,  width  of  mouth,  length  of 
nostril  and  of  eyelid,  size  of  feet  and  length  of  leg,  in  the 
wild  parent  species,  in  pouters,  fantails,  runts,  barbs, 
dragons,  carriers  and  tumblers.  Now,  some  of. these  birds, 
when  mature,  differ  in  so  extraordinary  a  manner  in  the 
length  and  form  of  beak,  and  in  other  P^aracters,  that  they 
would  certainly  have  been  ranked  ^'"distinct  genera  if 
found  in  a  state  of  nature.  But  when  the  nestling  birds 
of  these  several  breeds  were  placed  in  a  row,  though  most 
of  them  could  just  be  distinguished,  the  proportional  dif¬ 
ferences  in  the  above  specified  points  were  incomparably 
less  than  in  the  full-grown  birds.  Some  characteristic 
points  of  difference — for  instance,  that  of  the  width  of 
mouth — could  hardly  be  detected  in  the  young.  But  there 
was  one  remarkable  exception  to  this  rule,  for  the  young  of 
the  short-faced  tumbler  differed  from  the  young  of  the 
wild  rock-pigeon,  and  of  the  other  breeds,  in  almost  exactly 
the  same  proportions  as  in  the  adult  stage. 

These  facts  are  explained  by  the  above  two  principles. 
Fanciers  select  their  dogs,  horses,  pigeons,  etc.,  for  breed¬ 
ing,  when  nearly  grown  up.  They  are  indifferent  whether 
the  desired  qualities  are  acquired  earlier  or  later  in  life,  if 


DEVELOPMENT  AND  EMBRYOLOGY. 


463 


the  full-grown  animal  possesses  them.  And  the  cases  just 
given,  more  especially  that  of  the  pigeons,  show  that  the 
characteristic  differences  which  have  been  accumulated 
by  man’s  selection,  and  which  give  value  to  his  breeds, 
do  not  generally  appear  at  a  very  early  period  of  life,  and 
are  inherited  at  a  corresponding  not  early  period.  But  the 
case  of  the  short-faced  tumbler,  which  when  twelve  hours 
old  possessed  its  proper  characters,  proves  that  this  is  not 
the  universal  rule;  for  here  the  characteristic  differences 
must  either  have  appeared  at  an  earlier  period  than  usual, 
or,  if  not  so,  the  differences  must  have  been  inherited,  not 
at  a  corresponding,  but  at  an  earlier  age. 

Now,  let  us  apply  these  two  principles  to  species  in  a 
state  of  nature.  Let  us  take  a  group  of  birds,  descended 
from  some  ancient  form  and  modified  through  natural 
selection  for  different  habits.  Then,  from  the  many  slight 
successive  variations  having  supervened  in  the  several 
species  at  a  not  early  age,  and  having  been  inherited  at  a 
corresponding  age,  the  young  will  have  been  but  little 
modified,  and  they  will  still  resemble  each  other  much  more 
closely  than  do  the  adults,  just  as  we  have  seen  with  the 
breeds  of  the  pigeon.  We  may  extend  this  view  to  widely 
distinct  structures  and  to  whole  classes.  The  fore  limbs, 
for  instance,  which  once  served  as  legs  to  a  remote  progen¬ 
itor,  may  have  become,  through  a  long  course  of  modifica¬ 
tion,  adapted  in  one  descendant  to  act  as  hands,  in  another 
as  paddles,  in  another  as  wings;  but  on  the  above  two 
principles  the  fore  limbs  will  not  have  been  much  modified 
in  the  embryos  of  these  several  forms;  although  in  each 
form  the  fore  limb  will  differ  greatly  in  the  adult  state. 
Whatever  influence  long  continued  use  or  disuse  may  have 
had  in  modifying  the  limbs  or  other  parts  of  any  species, 
this  will  chiefly  or  solely  have  affected  it  when  nearly 
mature,  when  it  was  compelled  to  use  its  full  powers  to 
gain  its  own  living;  and  the  effects  thus  produced  will  have 
been  transmitted  to  the  offspring  at  a  corresponding  nearly 
mature  age.  Thus  the  young  will  not  be  modified,  or  will 
be  modified  only  in  a  slight  degree,  through  the  effects  of 
the  increased  use  or  disuse  of  parts. 

With  some  animals  the  successive  variations  may  have 
supervened  at  a  very  early  period  of  life,  or  the  steps  may 
have  been  inherited  at  an  earlier  age  than  that  at  which 


464 


DEVELOPMENT  AND  EMBRYOLOGY. 


they  first  occurred.  In  either  of  these  cases,  the  young  or 
embryo  will  closely  resemble  the  mature  parent-form,  as 
we  have  seen  with  the  short-faced  tumbler.  And  this  is 
the  rule  of  development  in  certain  whole  groups,  or  in 
certain  sub-groups  alone,  as  with  cuttle-fish,  land-shells, 
fresh-water  crustaceans,  spiders,  and  some  members  of 
the  great  class  of  insects.  With  respect  to  the  final 
cause  of  the  young  in  such  groups  not  passing  through 
any  metamorphosis,  we  can  see  that  this  would  follow 
from  the  following  contingencies:  namely,  from  the 
young  having  to  provide  at  a  very  early  age  for  their 
own  wants,  and  from  their  following  the  same  habits  of 
life  with  their  parents;  for  in  this  case  it  would  be  in¬ 
dispensable  for  their  existence  that  they  should  be  modified 
in  the  same  manner  as  their  parents.  Again,  with  respect 
to  the  singular  fact  that  many  terrestrial  and  fresh-water 
animals  do  not  undergo  any  metamorphosis,  while  marine 
members  of  the  same  groups  pass  through  various  trans¬ 
formations,  Fritz  Muller  has  suggested  that  the  process  of 
slowly  modifying  and  adapting  an  animal  to  live  on  the 
land  or  in  fresh  water,  instead  of  in  the  sea,  would  be 
greatly  simplified  by  its  not  passing  through  any  larval 
stage;  for  it  is  not  probable  that  places  well  adapted  for 
both  the  larval  and  mature  stages,  under  such  new  and 
greatly  changed  habits  of  life,  would  commonly  be  found 
unoccupied  or  ill-occupied  by  other  organisms.  In  this 
case  the  gradual  acquirement  at  an  earlier  and  earlier  age 
of  the  adult  structure  would  be  favored  by  natural  selec¬ 
tion;  and  all  traces  of  former  metamorphoses  would  finally 
be  lost. 

If,  on  the  other  hand,  it  profited  the  young  of  an  ani¬ 
mal  to  follow  habits  of  life  slightly  different  from  those  of 
the  parent-form,  and  consequently  to  be  constructed  on  a 
slightly  different  plan,  or  if  it  profited  a  larva  already  dif¬ 
ferent  from  its  parent  to  change  still  further,  then,  on  the 
principle  of  inheritance  at  corresponding  ages,  the  young 
or  the  larva?  might  be  rendered  by  natural  selection  more 
and  more  different  from  their  parents  to  any  conceivable 
extent.  Differences  in  the  larva  might,  also,  become  corre¬ 
lated  with  successive  stages  of  its  development;  so  that  the 
larva,  in  the  first  stage,  might  come  to  differ  greatly  from 
the  larva  in  the  second  stage,  as  is  the  case  with  many  ani* 


DEVELOPMENT  AND  EMBRYOLOGY . 


465 


mals.  The  adult  might  also  become  fitted  for  sites  or 
habits,  in  which  organs  of  locomotion  or  of  the  senses,  etc., 
would  be  useless;  and  in  this  case  the  metamorphosis 
would  be  retrograde. 

From  the  remarks  just  made  we  can  see  how  by  changes 
of  structure  in  the  young,  in  conformity  with  changed 
habits  of  life,  together  with  inheritance  at  corresponding 
ages,  animals  might  come  to  pass  through  stages  of  devel¬ 
opment,  perfectly  distinct  from  the  primordial  condition 
of  their  adult  progenitors.  Most  of  our  best  authorities 
are  now  convinced  that  the  various  larval  and  pupal  stages 
of  insects  have  thus  been  acquired  through  adaptation,  and 
not  through  inheritance  from  some  ancient  form.  The 
curious  case  of  Sitaris — a  beetle  which  passes  through  cer¬ 
tain  unusual  stages  of  development — will  illustrate  how 
this  might  occur.  The  first  larval  form  is  described  by  M. 
Fabre,  as  an  active,  minute  insect,  furnished  with  six  legs, 
two  long  antennae,  and  four  .eyes.  These  larvae  are 
hatched  in  the  nests  of  bees;  and  when  the  male  bees 
emerge  from  their  burrows,  in  the  spring,  which  they  do 
before  the  females,  the  larvae  spring  on  them,  and  after¬ 
ward  crawl  on  to  the  females  while  paired  with  the  males. 
As  soon  as  the  female  bee  deposits  her  eggs  on  the  surface 
of  the  honey  stored  in  the  cells,  the  larvae  of  the  Sitaris 
leap  on  the  eggs  and  devour  them.  Afterward  they 
undergo  a  complete  change;  their  eyes  disappear;  theirlegs 
and  antennae  become  rudimentary,  and  they  feed  on  honey; 
so  that  they  now  more  closely  resemble  the  ordinary  larvae 
of  insects;  ultimately  they  undergo  a  further  transforma¬ 
tion,  and  finally  emerge  as  the  perfect  beetle.  Now,  if  an 
insect,  undergoing  transformations  like  those  of  the 
Sitaris,  were  to  become  the  progenitor  of  a  whole  new  class 
of  insects,  the  course  of  development  of  the  new  class 
would  be  widely  different  from  that  of  our  existing  insects; 
and  the  first  larval  stage  certainly  would  not  represent  the 
former  condition  of  any  adult  and  ancient  form. 

On  the  other  hand  it  is  highly  probable  that  with  many 
animals  the  embryonic  or  larval  stages  show  us,  more  or 
less  completely,  the  condition  of  the  progenitor  of  the  whole 
group  in  its  adult  state.  In  the  great  class  of  the  Crus¬ 
tacea,  forms  wonderfully  distinct  from  each  other,  namely, 
suctorial  parasites,  cirripedes,  entomostraca,  and  even  the 


466  DEVELOPMENT  AND  EMBRYOLOGY. 

malacostraca,  appear  at  first  as  larvae  under  the  nauplius- 
form;  and  as  these  larvae  live  and  feed  in  the  open 
sea,  and  are  not  adapted  for  any  peculiar  habits  of 
life,  and  from  other  reasons  assigned  by  Fritz  Muller,  it 
is  probable  that  at  some  very  remote  period  an  independ¬ 
ent  adult  animal,  resembling  the  Nauplius,  existed,  and 
subsequently  produced,  along  several  divergent  lines  of 
descent,  the  above-named  great  Crustacean  groups.  So 
again,  it  is  probable,  from  what  we  know  of  the  embryos 
of  mammals,  birds,  fishes  and  reptiles,  that  these  animals 
are  the  modified  descendants  of  some  ancient  progenitor, 
which  was  furnished  in  its  adult  state  with  branchke,  a 
swim- bladder,  four  fin-like  limbs,  and  a  long  tail,  all  fitted 
for  an  aquatic  life. 

As  all  the  organic  beings,  extinct  and  recent,  which 
have  ever  lived,  can  be  arranged  within  a  few  great  classes; 
and  as  all  within  each  class  have,  according  to  our  theorv, 
been  connected  together  by  fine  gradations,  the  best,  and* 
if  our  collections  were  nearly  perfect,  the  only  possible 
arrangement  would  be  genealogical;  descent  "being  the 
hidden  bond  of  connection  which  naturalists  have  been 
seeking  under  the  term  of  the  Natural  System.  On  this 
view  we  can  understand  how  it  is  that,  in  the  eyes  of  most 
naturalists,  the  structure  of  the  embryo  is  even  more 
important  for  classification  than  that  of  the  adult.  In 
two  or  more  groups  of  animals,  however  much  they  may 
differ  from  each  other  in  structure  and  habits  in  their 
adult  condition,  if  they  pass  through  closely  similar 
embryonic  stages,  we  may  feel  assured  that  they  all  are 
descended  from  one  parent-form,  and  are  therefore  closely 
related.  Thus,  community  in  embryonic  structure  reveals 
community  of  descent;  but  dissimilarity  in  embryonic 
development  does  not  prove  discommunity  of  descent,  for 
in  one  of  two  groups  the  developmental  stages  may  have 
been  suppressed,  or  may  have  been  so  greatly  modified 
through  adaptation  to  new  habits  of  life  as  to  be  no  longer 
recognizable.  Even  in  groups,  in  which  the  adults  have 
been  modified  to  an  extreme  degree,  community  of  origin 
is  often  revealed  by  the  structure  of  the  larvae;  we  have 
seen,  for  instance,  that  cirripedes,  though  externally  so  like 
shell-fish,  are  at  once  known  by  their  larvas  to  belong  to 
the  great  class  of  crustaceans.  As  the  embryo  often  shows 


DEVELOPMENT  AND  EMBH YOLOG  T.  467 

ns  more  or  less  plainly  the  structure  of  the  less  modified 
d.nd  ancient  progenitor  of  the  group,  we  can  see  why  ancient 
and  extinct  forms  so  often  resemble  in  their  adult  state  the 
embryos  of  existing  species  of  the  same  class.  Agassiz 
believes  this  to  be  a  universal  law  of  nature;  and  we  mav 
hope  hereafter  to  see  the  law  proved  true.  It  can,  how¬ 
ever,  be  proved  true  only  in  those  cases  in  which  the 
ancient  state  of  the  progenitor  of  the  group  has  not  been 
wholly  obliterated,  either  by  successive  variations  having 
supervened  at_a  very  early  period  of  growth,  or  by  such 
variations  having  been  inherited  at  an  earlier  age  than  that 
at  which  they  first  appeared.  It  should  also  be  borne  in 
mind,  that  the  law  may  be  true,  but  yet,  owing  to  the 
geological  record  not  extending  far  enough  back  in  time, 
may  remain  for  a  long  period,  or  for  ever,  incapable  of 
demonstration.  The  law  will  not  strictly  hold  good  in 
those  cases  in  which  an  ancient  form  became  adapted  in 
its  larvae  state  to  some  special  line  of  life,  and  transmitted 
the  same  larval  state  to  a  whole  group  of  descendants;  for 
such  larval  will  not  resemble  any  still  more  ancient  form 
in  its  adult  state. 

Thus,  as  it  seems  to  me,  the  leading  facts  in  embryology, 
which  are  second  to  none  in  importance,  are  explained  on 
the  principle  of  variations  in  the  many  descendants  from 
some  one  ancient  progenitor,  having  appeared  at  a  not 
very  early  period  of  life,  and  having  been  inherited  at  a 
corresponding  period.  Embryology  rises  greatly  in  inter¬ 
est,  when  we  look  at  the  embryo  as  a  picture,  more  or  less 
obscured,  of  the  progenitor,  either  in  its  adult  or  larval 
state,  of  all  the  members  of  the  same  great  class. 

RUDIMENTARY,  ATROPHIED,  AND  ABORTED  ORGANS. 

Organs  or  parts  in  this  strange  condition,  bearing  the 
plain  stamp  of  inutility,  are  extremely  common,  or  even 
general,  throughout  nature.  It  would  be  impossible  to 
name  one  of  the  higher  animals  in  which  some  part  or 
other  is  not  in  a  rudimentary  condition.  In  the  mamma¬ 
lia,  for  instance,  the  males  possess  rudimentary  mammas; 
in  snakes  one  lobe  of  the  lungs  is  rudimentary;  in  birds 
the  ii  bastard- wing  ”  may  safely  be  considered  as  a  rudir 
mentary  digit,  and  in  some  species  the  whole  wing  is  so  fa- 


46S 


RUDIMENTARY ,  ATROPHIED , 


rudimentary  that  it  cannot  be  used  for  flight.  What  can 
be  more  curious  than  the  presence  of  teeth  in  foetal  whales, 
which  when  grown  up  have  not  a  tooth  in  their  heads;  or 
the  teeth,  which  never  cut  through  the  gums,  in  the  upper 
jaws  of  unborn  calves? 

Rudimentary  organs  plainly  declare  their  origin  and 
meaning  in  various  ways.  There  are  beetles  belonging  to 
closely  allied  species,  or  even  to  the  same  identical  species, 
which  have  either  full-sized  and  perfect  wings,  or  mere 
rudiments  of  membrane,  which  not  rarely  lie  under  wing- 
covers  firmly  soldered  together;  and  in  these  cases  it  is  im¬ 
possible  to  doubt,  that  the  rudiments  represent  wings. 
Rudimentary  organs  sometimes  retain  their  potentiality: 
this  occasionally  occurs  with  the  mammae  of  male  mammals, 
which  have  been  known  to  become  well  developed  and  to 
secrete  milk.  So  again  in  the  udders  in  the  genus  Bos, 
there  are  normally  four  developed  and  two  rudimentary 
teats;  but  the  latter  in  our  domestic  cows  sometimes  be¬ 
come  well  developed  and  yield  milk.  In  regard  to  plants, 
the  petals  are  sometimes  rudimentary,  and  sometimes  well 
developed  in  the  individuals  of  the  same  species.  In  cer¬ 
tain  plants  having  separated  sexes  Kolreuter  found  that  by 
crossing  a  species,  in  which  the  male  flowers  included 
a  rudiment  of  a  pistil,  with  an  hermaphrodite  species, 
having  of  course  a  well-developed  pistil,  the  rudiment  in 
the  hybrid  offspring  was  much  increased  in  size;  and  this 
clearly  shows  that  the  rudimentary  and  perfect  pistils  are 
essentially  alike  in  nature.  An  animal  may  possess  vari¬ 
ous  parts  in  a  perfect  state,  and  yet  they  may  in  one  sense 
be  rudimentary,  for  they  are  useless:  thus  the  tadpole  of 
the  common  salamander  or  water-newt,  as  Mr.  G.  H. 
Lewes  remarks,  “  has  gills,  and  passes  its  existence  in  the 
water;  but  the  Salamandra  atra,  which  lives  high  up 
among  the  mountains,  brings  forth  its  young  full-formed. 
This  animal  never  lives  in  the  water.  Yet  if  we  open  a 
gravid  female,  we  find  tadpoles  inside  her  with  exquisitely 
feathered  gills;  and  when  placed  in  water  they  swim  about 
like  the  tadpoles  of  the  water-newt.  Obviously  this  aquatic 
organization  has  no  reference  to  the  future  life  of  the 
animal,  nor  has  it  any  adaptation  to  its  embryonic  con¬ 
dition;  it  has  solely  reference  to  ancestral  adaptations,  it 
repeats  a  phase  in  the  development  of  its  progenitors. ” 


AND  ABORTED  ORGANS. 


469 


An  organ,  serving  for  two  purposes,  may  become  rudi¬ 
mentary  or  utterly  aborted  for  one,  even  the  more  impor¬ 
tant  purpose,  and  remain  perfectly  efficient  for  the  other. 
Thus,  in  plants,  the  office  of  the  pistil  is  to  allow  the  pollen - 
tubes  to  reach  the  ovules  within  the  ovarium.  The  pistil 
consists  of  a  stigma  supported  on  a  style;  but  in  some  Com¬ 
posite,  the  male  florets,  which  of  course  cannot  be  fecun¬ 
dated,  have  a  rudimentary  pistil,  for  it  is  not  crowned  with 
a  stigma;  but  the  style  remains  well  developed  and  is 
clothed  in  the  usual  manner  with  hairs,  which  serve  to 
brush  the  pollen  out  of  the  surrounding  and  conjoined 
anthers.  Again,  an  organ  may  become  rudimentary  for 
its  proper  purpose,  and  be  used  for  a  distinct  one:  in  cer¬ 
tain  fishes  the  swim-bladder  seems  to  be  rudimentary  for 
its  proper  function  of  giving  buoyancy,  but  has  become 
converted  into  a  nascent  breathing  organ  or  lung.  Many 
similar  instances  could  be  given. 

Useful  organs,  however  little  they  may  be  developed, 
unless  we  have  reason  to  suppose  that  they  were  formerly 
more  highly  developed,  ought  not  to  be  considered  as 
rudimentary.  They  may  be  in  a  nascent  condition,  and  in 
progress  toward  further  development.  Rudimentary 
organs,  on  the  other  hand,  are  either  quite  useless,  such  as 
teeth  which  never  cut  through  the  gums,  or  almost  useless, 
such  as  the  wings  of  an  ostrich,  which  serve  merely  as 
sails.  As  organs  in  this  condition  would  formerly,  when  still 
less  developed,  have  been  of  even  less  use  than  at  present, 
they  cannot  formerly  have  been  produced  through  varia¬ 
tion  and  natural  selection,  which  acts  solely  by  the  preser¬ 
vation  of  useful  modifications.  They  have  been  partially 
retained  by  the  power  of  inheritance,  and  relate  to  a 
former  state  of  things.  It  is,  however,  often  difficult  to 
distinguish  between  rudimentary  and  nascent  organs;  for 
we  can  judge  only  by  analogy  whether  a  part  is  capable  of 
further  development,  in  which  case  alone  it  deserves  to  be 
called  nascent.  Organs  in  this  condition  will  always  be 
somewhat  rare;  for  beings  thus  provided  will  commonly 
have  been  supplanted  by  their  successors  with  the  same 
organ  in  a  more  perfect  state,  and  consequently  will  have 
become  long  ago  extinct.  The  wing  of  the  penguin  is  of 
high  service,  acting  as  a  fin;  it  may,  therefore,  represent 
the  nascent  state  of  the  wing:  not  that  I  believe  this  to  be 


470 


RUDIMENTARY ,  ATROPHIED , 


the  case;  it  is  more  probably  a  reduced  organ,  modified 
for  a  new  function:  the  wing  of  the  Apteryx,  on  the  other 
hand,  is  quite  useless,  and  is  truly  rudimentary.  Owen 
considers  the  simple  filamentary  limbs  of  the  Lepidosiren 
as  the  “beginnings  of  organs  which  attain  full  functional 
development  in  higher  vertebrates;  ”  but,  according  to  the 
view  lately  advocated  by  Dr.  Gunther,  they  are  probably 
remnants,  consisting  of  the  persistent  axis  of  a  fin,  with 
the  lateral  rays  or  branches  aborted.  The  mammary  glands 
of  the  Ornithorhynchus  may  be  considered,  in  comparison 
with  the  udders  of  a  cow,  as  in  a  nascent  condition.  The 
ovigerous  frena  of  certain  cirripedes,  which  have  ceased  to 
give  attachment  to  the  ova  and  are  feebly  developed,  are 
nascent  branchiae. 

Rudimentary  organs  in  the  individuals  of  the  same 
species  are  very  liable  to  vary  in  the  degree  of  their  devel-  ' 
opment  and  in  other  respects.  In  closely  allied  species, 
also,  the  extent  to  which  the  same  organ  has  been  reduced 
occasionally  differs  much.  This  latter  fact  is  well  exem¬ 
plified  in  the  state  of  the  wings  of  female  moths  belonging 
to  the  same  family.  Rudimentary  organs  may  be  utterly 
aborted;  and  this  implies,  that  in  certain  animals  or 
plants,  parts  are  entirely  absent  which  analogy  would 
lead  us  to  expect  to  find  in  them,  and  which  are  occasion¬ 
ally  found  in  monstrous  individuals.  Thus  in  most  of  the 
Scrophulariacese  the  fifth  stamen  is  utterly  aborted;  yet  we 
may  conclude  that  a  fifth  stamen  once  existed,  for  a  rudi¬ 
ment  of  it  is  found  in  many  species  of  the  family,  and  this 
rudiment  occasionally  becomes  perfectly  developed,  as  may 
sometimes  be  seen  in  the  common  snap-dragon.  In  tracing 
the  homologies  of  any  part  in  different  members  of  the 
same  class,  nothing  is  more  common,  or,  in  order  fully  to 
understand  the  relations  of  the  parts,  more  useful  than  the 
discovery  of  rudiments.  This  is  well  shown  in  the  draw¬ 
ings  given  by  Owen  of  the  leg  bones  of  the  horse,  ox  and 
rhinoceros. 

It  is  an  important  fact  that  rudimentary  organs,  such  as 
teeth  in  the  upper  jaws  of  whales  and  ruminants,  can  often 
be  detected  in  the  embryo,  but  afterward  wholly  disappear. 
It  is  also,  I  believe,  a  universal  rule,  that  a  rudimentary 
part  is  of  greater  size  in  the  embryo  relatively  to  the  ad¬ 
joining  parts,  than  in  the  adult;  so  that  the  organ  at  this 


AND  ABORTED  ORGANS. 


471 


early  age  is  less  rudimentary,  or  even  cannot  be  said  to  be 
in  any  degree  rudimentary.  Hence  rudimentary  organs  in 
the  adult  are  often  said  to  have  retained  their  embryonic 
condition. 

I  have  now  given  the  leading  facts  with  respect  to  rudi¬ 
mentary  organs.  In  reflecting  on  them,  every  one  must  be 
struck  with  astonishment;  for  the  same  reasoning  power 
which  tells  us  that  most  parts  and  organs  are  exquisitely 
adapted  for  certain  purposes,  tells  us  with  equal  plainness 
that  these  rudimentary  or  atrophied  organs  are  imperfect 
and  useless.  In  works  on  natural  history,  rudimentary 
organs  are  generally  said  to  have  been  created  “for  the 
sake  of  symmetry,”  or  in  order  “  to  complete  the  scheme 
of  nature.”  But  this  is  not  an  explanation,  merely 
a  re-statement  of  the  fact.  Nor  is  it  consistent  with  itself: 
thus  the  boa-constrictor  has  rudiments  of  hind  limbs  and 
of  a  pelvis,  and  if  it  be  said  that  these  bones  have  been  re¬ 
tained  “to  complete  the  scheme  of  nature,”  why,  as  Pro¬ 
fessor  Weismann  asks,  have  they  not  been  retained  by  other 
snakes,  which  do  not  possess  even  a  vestige  of  these  same 
bones?  What  would  be  thought  of  an  astronomer  who 
maintained  that  the  satellites  revolve  in  elliptic  courses 
round  their  planets  “for  the  sake  of  symmetry,”  because 
the  planets  thus  revolve  round  the  sum?  An  eminent 
physiologist  accounts  for  the  presence  of  rudimentary 
organs,  by  supposing  that  they  serve  to  excrete  matter  in 
excess,  or  matter  injurious  to  the  system;  but  can  we  sup¬ 
pose  that  the  minute  papilla,  which  often  represents  the 
pistil  in  male  flowers,  and  which  is  formed  of  mere  cellular 
tissue,  can  thus  act?  (Jan  we  suppose  that  rudimentary 
teeth,  which  are  subsequently  absorbed,  are  beneficial  to 
the  rapidly  growing  embryonic  calf  by  removing  matter  so 
precious  as  phosphate  of  lime?  When  a  man’s  fingers  have 
been  amputated,  imperfect  nails  have  been  known  to  ap¬ 
pear  on  the  stumps,  and  I  could  as  soon  believe  that  these 
vestiges  of  nails  are  developed  in  order  to  excrete  horny 
matter,  as  that  the  rudimentary  nails  on  the  fin  of  the 
manatee  have  been  developed  for  this  same  purpose. 

On  the  view  of  descent  with  modification,  the  origin  of 
rudimentary  organs  is  comparatively  simple;  and  we  can 
understand  to  a  large  extent  the  laws  governing  tlieit 
imperfect  development.  We  have  plenty  of  cases  of  rudi- 


473 


RUDIMENTARY \  ATROPHIED , 


mentary  organs  in  our  domestic  productions,  as  the  stump 
of  a  tail  in  tailless  breeds,  the  vestige  of  an  ear  in 
earless  breeds  of  sheep— the  reappearance  of  minute  dang¬ 
ling  horns  in  hornless  breeds  of  cattle,  more  especially, 
according  to  Youatt,  in  young  animals— and  the  state  of 
the  whole  flower  in  the  cauliflower.  We  often  see  rudi¬ 
ments  of  various  parts  in  monsters;  but  I  doubt  whether 
any  of  these  cases  throw  light  on  the  origin  of  rudimentary 
organs  in  a  state  of  nature,  further  than  by  showing  that 
rudiments  can  be  produced;  for  the  balance  of  evidence 
clearly  indicates  that  species  under  Jiature  do  not  undergo 
great  and  abrupt  changes.  But  we  learn  from  the  study 
of  our  domestic  productions  that  the  disuse  of  parts  leads 
to  their  reduced  size;  and  that  the  result  is  inherited. 

It  appears  probable  that  disuse  has  been  the  main  agent 
in  rendering  organs  rudimentary.  It  would  at  first  lead 
by  slow  steps  to  the  more  and  more  complete  reduction  of 
a  part,  until  at  last  it  became  rudimentary — as  in  the  case 
of  the  eyes  of  animals  inhabiting  dark  caverns,  and  of  the 
wings  of  birds  inhabiting  oceanic  islands,  which  have 
seldom  been  forced  by  beasts  of  prey  to  take  flight,  and 
have  ultimately  lost  the  power  of  flying.  Again,  an  organ, 
useful  under  certain  conditions,  might  become,  injurious 
under  others,  as  with  the  wings  of  beetles  living  on  small 
and  exposed  islands;  and  in  this  case  natural  selection  will 
have  aided  in  reducing  the  organ,  until  it  was  rendered 
harmless  and  rudimentary. 

Any  change  in  structure  and  function,  which  can  be 
effected  by  small  stages,  is  within  the  power  of  natural 
selection;  so  that  an  organ  rendered,  through  changed 
habits  of  life,  useless  or  injurious  for  one  purpose,  might 
be  modified  and  used  for  another  purpose.  An  organ 
might,  also,  be  retained  for  one  alone  of  its  former  func¬ 
tions.  Organs,  originally  formed  by  the  aid  of  natural 
selection,  when  rendered  useless  may  well  be  variable,  for 
their  variations  can  no  longer  be  checked  by  natural  selec¬ 
tion.  All  this  agrees  well  with  what  we  see  under  nature. 
Moreover,  at  whatever  period  of  life  either  disuse  or  selection 
reduces  an  organ,  and  this  will  generally  be  when  the  being 
has  come  to  maturity  and  has  to  exert  its  full  powers  of 
action,  the  principle  of  inheritance  at  corresponding  ages 
will  tend  to  reproduce  the  organ  in  its  reduced  state  at  the 


AND  ABORTED  ORGANS. 


473 


same  mature  age,  but  will  seldom  affect  it  in  the  embryo. 
Thus  we  can  understand  the  greater  size  of  rudimentary 
organs  in  the  embryo  relatively  to  the  adjoining  parts,  and 
their  lesser  relative  size  in  the  adult.  If,  for  instance,  the 
digit  of  an  adult  animal  was  used  less  and  less  during 
many  generations,  owing  to  some  change  of  habits,  or  if  an 
organ  or  gland  was  less  and  less  functionally,  exercised,  we 
may  infer  that  it  would  become  reduced  in  size  in  the 
adult  descendants  of  this  animal,  but  would  retain  nearly 
its  original  standard  of  development  in  the  embryo. 

There  remains,  however,  this  difficulty.  After  an  organ 
has  ceased  being  used,  and  has  become  in  consequence 
much  reduced,  how  can  it  be  still  further  reduced  in  size 
until  the  merest  vestige  is  left;  and  how  can  it  be  finally 
quite  obliterated?  It  is  scarcely  possible  that  disuse  can 
go  on  producing  any  further  effect  after  the  organ  has 
once  been  rendered  functionless.  Some  additional  ex¬ 
planation  is  here  requisite  which  I  cannot  give.  If,  for 
instance,  it  could  be  proved  that  every  part  of  the  organ¬ 
ization  tends  to  vary  in  a  greater  degree  toward  diminution 
than  toward  augmentation  of  size,  then  we  should  be  able 
to  understand  how  an  organ  which  has  become  useless 
would  be  rendered,  independently  of  the  effects  of  disuse, 
rudimentary  and  would  at  last  be  wholly  suppressed;  for 
the  variations  toward  diminished  size  would  no  longer  be 
checked  by  natural  selection.  The  principle  of  the  economy 
of  growth,  explained  in  a  former  chapter,  by  which  the 
materials  forming  any  part,  if  not  useful  to  the  possessor, 
are  saved  as  far  as  is  possible,  will  perhaps  come  into  play 
in  rendering  a  useless  part  rudimentary.  But  this  prin¬ 
ciple  will  almost  necessarially  be  confined  to  the  earlier  stages 
of  the  process  of  reduction;  for  we  cannot  suppose  that  a 
minute  papilla,  for  instance,  representing  in  a  male  flowei 
the  pistil  of  the  female  flower,  and  formed  merely  of  cellu- 
lai  tissue,  could  be  further  reduced  or  absorbed  for  the 
sake  of  economizing  nutriment. 

Finally,  as  rudimentary  organs,  by  whatever  steps  they 
may  have  been  degraded  into  their  present  useless  condi¬ 
tion,  are  the  record  of  a  former  state  of  things,  and  have 
been  retained  solely  through  the  power  of  inheritance — we 
can  understand,  on  the  genealogical  view  of  classification, 
how  it  is  that  systematists,  in  placing  organisms  in  their 


474 


SUMMARY. 


proper  places  in  the  natural  system,  have  often  found  rudi- 
mentaiy  parts  as  useful  as,  or  even  sometimes  more  useful 
than,  paits  of  high  physiological  importance.  Rudimentary 
organs  may  be  compared  with  the  letters  in  a  word,  still 
retained  in  the  spelling,  but  become  useless  in  the  pro¬ 
nunciation,  but  which  serve  as  a  clue  for  its  derivation. 
On  the  view  of  descent  with  modification,  we  may  conclude 
that  the  existence  of  organs  in  a  rudimentary,  imperfect, 
and  useless  condition,  or  quite  aborted,  far  from  presenting 
a  strange  difficulty,  as  they  assuredly  do  on  the  old  doctrine 
of  creation,  might  even  have  been  anticipated  in  accordance 
with  the  views  here  explained. 

SUMMARY. 

In  this  chapter  I  have  attempted  to  show  that  the 
arrangement  of  all  organic  beings  throughout  all  time  in 
groups  under  groups— that  the  nature  of  the  relationships 
by  which  all  living  and  extinct  organisms  are  united  by 
complex,  radiating,  and  circuituous  lines  of  affinities  into 
a  few  grand  classes— the  rules  followed  and  the  difficulties 
encountered  by  naturalists  in  their  classifications — the 
value  set  upon  characters,  if  constant  and  prevalent, 
whether  of  high  or  of  the  most  trifling  importance,  or,  as 
with  rudimentary  organs  of  no  importance— the  wide 
opposition  in  value  between  analogical  or  adaptive  charac- 
teis,  and  characters  of  true  affinity ;  and  other  such  rules j 
—all  naturally  follow  if  we  admit  the  common  parentage 
of  allied  forms,  together  with  their  modification  through 
vanation  and  natural  selection,  with  the  contingencies  of 
extinction  and  divergence  of  character.  In  considering 
this  view  of  classification,  it  should  be  borne  in  mind  that 
the  element  of  descent  has  been  universally  used  in  rank- 
ing  together  the  sexes,  ages,  dimorphic  forms,  and  acknowl¬ 
edged  \  arieties  of  the  same  species,  however  much  they 
may  differ  from  each  other  in  structure  If  we  extend  the 
use  of  this  element  of  descent— the  one  certainly  known 
cause  of  similarity  in  organic  beings— we  shall  understand 
what  is  meant  by  the  Natural  System:  it  is  genealogical 
in  its  attempted  arrangement,  with  the  grades  of  acquired 
difference  marked  by  the  terms,  varieties,  species,  genera, 
families,  orders,  and  classes.  ° 


SUMMARY. 


475 


On  this  same  view  of  descent  with  modification,  most 
of  the  great  facts  in  Morphology  become  intelligible — 
whether  we  look  to  the  same  pattern  displayed  by  the 
different  species  of  the  same  class  in  their  homologous 
organs,  to  whatever  purpose  applied ;  or  to  the  serial  and 
lateral  homologies  in  each  individual  animal  and  plant. 

On  the  principle  of  successive  slight  variations,  not 
necessarily  or  generally- supervening  at  a  very  early  period 
of  life,  and  being  inherited  at  a  corresponding  period,  we 
can  understand  the  leading  facts  in  embryology;  namely, 
the  close  resemblance  in  the  individual  embryo  of  the  parts 
which  are  homologous,  and  which  when  matured  become 
widely  different  in  structure  and  function;  and  the  resem¬ 
blance  of  the  homologous  parts  or  organs  in  allied  though 
distinct  species,  though  fitted  in  the  adult  state  for  habits 
as  different  as  is  possible.  Larvae  are  active  embryos, 
which  have  been  specially  modified  in  a  greater  or  less 
degree  in  relation  to  their  habits  of  life,  with  their  modifi¬ 
cations  inherited  at  a  corresponding  early  age.  On  these 
same  principles,  and  bearing  in  mind  that  when  organs 
are  reduced  in  size,  either  from  disuse  or  through  natural 
selection,  it  will  generally  be  at  that  period  of  life  when 
the  being  has  to  provide  for  its  own  wants,  and  bearing  in 
in  mind  how  strong  is  the  force  of  inheritance — the  occur¬ 
rence  of  rudimentary  organs  might  even  have  been  antici¬ 
pated.  The  importance  of  embryological  characters  and 
of  rudimentary  organs  in  classification  is  intelligible,  on 
the  view  that  a  natural  arrangement  must  be  genealogical. 

Finally,  the  several  classes  of  facts  which  have  been  con¬ 
sidered  in  this  chapter,  seem  to  me  to  nroclaim  so  plainly, 
that  the  innumerable  species,  genera  and  families,  with 
which  this  world  is  peopled,  are  all  descended,  each 
within  its  own  class  or  group,  from  common  parents,  and 
have  all  been  modified  in  the  course  of  descent,  that  I 
should  without  hesitation  adopt  this  view,  even  if  it  were 
unsupported  by  other  facts  or  arguments. 


-176 


RECAPITULA  TION. 


CHAPTER  XV. 

RECAPITULATION  AND  CONCLUSION. 

Recapitulation  of  the  objections  to  the  theory  of  Natural  Selection _ 

Recapitulation  of  the  general  and  special  circumstances  in  its 
favor — Causes  of  the  general  belief  in  the  immutability  of 
species — How  far  the  theory  of  Natural  Selection  may  he 
extended — Effects  of  its  adoption  on  the  study  of  Natural 
History — Concluding  remarks. 

As  this  whole  volume  is  one  long  argument,  it  may  be 
convenient  to  the  reader  to  have  the  leading  facts  and 
inferences  briefly  recapitulated. 

^  That  many  and  serious  objections  may  be  advanced 
against  the  theory  of  descent  with  modification  through 
variation  and  natural  selection,  I  do  not  deny.  I  have  en¬ 
deavored  to  give  to  them  their  full  force.  Nothing  at  first 
can  appear  more  difficult  to  believe  than  that  the  more 
complex  organs  and  instincts  have  been  perfected,  not  by 
means  superior  to,  though  analogous  with,  human  reason, 
but  by  the  accumulation  of  innumerable  slight  variations, 
each  good  for  the  individual  possessor.  Nevertheless,  this 
difficulty,  though  appearing  to  our  imagination  insuper¬ 
ably  great,  can  not  be  considered  real  if  we  admit  the  fol¬ 
lowing  propositions,  namely,  that  all  parts  of  tha  nrgm,i_ 
zation  and  instincts  offer.  at  least,  individual  differences — 
that  there  is  a  struggle  for  existence  leading  to" the  nrescr- 
vation  of  profitable  deviations  of  structureor  instinct^ 
and,  lastly,  that  gradations  in  the  stufp.  of  perfccth^Thf 
each  organ  may  have  existed,  each  good  of  its  kind.  The 
truth  of  these  propositions  can  not,  I  think,  be  disputed. 

It  is,  no  doubt,  extremely  difficult  even  to  conjecture 
by  what  gradations  many  structures  have  been  perfected, 
more  especially  among  broken  and  failing  groups  of 
organic  beings,  which  have  suffered  much  extinction;  but 
x  we  see  so  many  strange  gradations  in  nature,  that  we  ought 


RECAP  ITU  LA  TION. 


47? 


tube  extremely  cautious  in  saving  thftt  any:  organ  or  in¬ 
stinct,  or  any  whole  structure,  could  not  have  arrived  at 
its  present  state  by  m aiTy'  gi’adu'a te TlffepsT  Th ere*  arc,  it 
must  be  admitted,  cases  of  special  difficulty  opposed  to  the 
theory  of  natural  selection:  and  one  of  the  most  curious  of 
these  is  the  existence  in  the  same  community  of  two  or 
three  defined  castes  of  workers  or  sterile  female  ants;  but  I 
have  attempted  to  show  how  these  difficulties  can  be 
mastered. 

With  respect  to  the  almost  universal  sterility  of  species 
when  first  crossed,  which  forms  so  remarkable  a  contrast 
with  the  almost  universal  fertility  of  varieties  when  crossed, 
I  must  refer  the  reader  to  the  recapitulation  of  the  facts 
given  at  the  end  of  the  ninth  chapter,  which  seem  to  me 
conclusively  to  show  that  this  sterility  is  no  more  a  special 
endowment  than  is  the  incapacity  of  two  distinct  kinds 
of  trees  to  be  grafted  together;  but  that  it  is  incidental  on 
differences  confined  to  the  reproductive  systems  of  the  in¬ 
tercrossed  species.  We  see  the  truth  of  this  conclusion  in 
the  vast  difference  in  the  results  of  crossing,  the  same  two 
species  reciprocally — that  is,  when  one  species  is  first  used 
as  the  father  and  then  as  the  mother.  Analogy  from  the 
consideration  of  dimorphic  and  trimorphic  plants  clearly 
leads  to  the  same  conclusion,  for  when  the  forms  are 
illegitimately  united,  they  yield  few  or  no  se  ,  ( 

offspring  are  more  or  less  sterile;  and  these  forms  belong 
to  the  same  undoubted  species.,  and  differ  from  each  other 
in  no  respect  except  in  their  reproductive  organs  and 
functions. 

Although  the  fertility  of  varieties  when  intercrossed,  and 
of  their  mongrel  offspring,  has  been  asserted  by  so  many 
authors  to  be  universal,  this  cannot  be  considered  as  quite 
correct  after  the  facts  given  on  the  high  authority  of  Gart¬ 
ner  and  Kolreuter.  Most  of  the  varieties  which  have  been 
experimented  on  have  been  produced  under  domestication; 
and  as  domestication  (I  do  not  mean  mere  confinement) 
almost  certainly  tends  to  eliminate  that  sterility  which, 
judging  from  analogy,  would  have  affected  the  parent-spe¬ 
cies  if  intercrossed,  we  ought  not  to  expect  that  domesti¬ 
cation  would  likewise  induce  sterility  in  their  modified 
descendants  when  crossed.  This  elimination  of  sterility 
apparently  follows  from  the  same  cause  which  allows  ou.y 


478  RECAPITULATION, 

domestic  animals  to  breed  freely  under  diversified  circum¬ 
stances;  and  this  again  apparently  follows  from  their 
having  been  gradually  accustomed  to  frequent  changes  in 
their  conditions  of  life.  6 

A  double  and  parallel  series  of  facts  seems  to  throw  much 
light  on  the  sterility  of  species,  when  first  crossed,  and  of 
their  hybrid  offspring.  On  the  one  side,  there  is  good 
reason  to  believe  that  slight  changes  in  the  conditions  of 
lite  give  vigor  and  fertility  to  all  organic  beings.  We  know 
also  that  a  cross  between  the  distinct  individuals  of  the 
same  variety  and  between  distinct  varieties,  increases  the 
number  of  their  offspring,  and  certainly  gives  to  them  in¬ 
creased  size  and  vigor.  This  is  chiefly  owing  to  the  forms 
winch  are  crossed  having  been  exposed  to  somewhat  dif¬ 
ferent  conditions  of  life  ;  fori  have  ascertained  by  a  labori¬ 
ous  series  of  experiments  that  if  all  the  individuals  of  the 
same  variety  be  subjected  during  several  generations  to  the 
came  conditions,  the  good  derived  from  crossing  is  often 
much  diminished  or  wholly  disappears.  This  is  one  side  of 
the  case.  On  the  other  side,  we  know  that  species  which 
have  long  been  exposed  to  nearly  uniform  conditions,  when 
they  are  subjected  under  confinement  to  new  and  greatly 
changed  conditions,  either  perish,  or  if  they  survive,  are 
rendered  sterile,  though  retaining  perfect  health.  This 
does  not  occur,  or  only  in  a  very  slight  degree,  with  our 
domesticated  productions,  which  have  long  been  exposed 
to  fluctuating  conditions.  Hence  when  we  find  that  hybrids 
produced  by  a  cross  between  two  distinct  species  are  few  in 
number,  owing  to  their  perishing  soon  after  conception  or 
at  a  very  early  age,  or  if  surviving  that  they  are  rendered 
more  or  less  sterile,  it  seems  highly  probable  that  this 
result  is  due  to  their  having  been  in  fact  subjected  to  a  great 
change  in  their  conditions  of  life,  from  being  compounded 
ot  two  distinct  organizations.  He  who  will  explain  in  a 
definite  manner  why,  for  instance,  an  elephant  or  a  fox  will 
not  breed  under  confinement  in  its  native  country,  whilst 
,.e  domestic  pig  or  dog  will  breed  freely  under  the  most 
diversified  conditions,  will  at  the  same  time  be  able  to  give 
a  definite  answer  to  the  question  why  two  distinct  species, 
when  crossed,  as  well  as  their  hybrid  offspring,  are  gener¬ 
ally  rendered  more  or  less  sterile,  while  two  domesticated 

Cr°SSed  aud  tlieir  mouSrel  offspring  are  per- 


RECAPITULA  TION. 


479 


Turning  to  geographical  distribution,  the  difficulties  en¬ 
countered  on  the  theory  of  descent  with  modification 
are  serious  enough.  All  the  individuals  of  the  same 
species,  and  all  the  species  of  the  same  genus,  or  even 
higher  group,  are  descended  from  common  parents;  and 
therefore,  in  however  distant  and  isolated  parts  of  the 
world  they  may  now  be  found,  they  must  in  the  course  of 
successive  generations  have  traveled  from  some  one  point 
to  all  the  others.  We  are  often  wholly  unable  even  to  con¬ 
jecture  how  this  could  have  been  effected.  Yet.  as  we  have 
reason  to  believe  that  some  species  have  retained  the  same 
specific  form  for  very  long  periods  of  time,  immensely  long 
as  measured  by  years,  too  innch  stress  ought  not  to.be  laid 
on  the  occasional  wide  diffusion  of  the  same  species;  for 
during  very  long  periods  there  will  always  have  been  a 
good  chance  for  wide  migration  by  many  means.  A  broken 
or  interrupted  range  may  often  be  accounted  for  by  the  ex¬ 
tinction  of  the  species  in  the  intermediate  regions.  It  can 
not  be  denied  that  we  are  as  yet  very  ignorant  as  to  the  full 
extent  of  the  various  climatical  and  geographical  changes 
which  have  affected  the  earth  during  modern  periods;  and 
such  changes  will  often  have  facilitated  migration.  As  an 
example,  t have  attempted  to  show  how  potent  has  been  the 
influence  of  the  Glacial  period  on  the  distribution  oJLJhe 
sfl.rrm~fl.nri  of  afiiefl  snecies 'Throughout  the  world.  We  are 
as  yet  profoundly  ignorant  of  the  many  occasional  means 
of  transport.  With  respect  to  distinct  species  of  the  same 
genus,  inhabiting  distant  and  isolated  regions,  as  the  pro¬ 
cess  of  modification  has  necessarily  been  slow,  all  the 
means  of  migration  will  have  been  possible  during  a  very 
long  period;  and  consequently  the  difficulty  of  the  wide 
diffusion  of  the  species  of  the  same  genus  is  in  some  degree 


lessened. 

As  according  to  the  theory  of  natural  selection  an  inter¬ 
minable  n n mher~dTTntermediate  forms  must  have  existed", 
TTp¥rng~together  all  the  species  in  eanh  group  bv -gradations 
as  fineas  our  existing  varieties,  it  mav  he  asked.  Why  do  we 
not~see~ these  linking  forms  ail  around  us?  Why  are  not  all 
organic  beings  blended  together  in  an  inextricable  chaos? 
With  respect  to  existing  forms,  we  should  remember  that 
we  have  no  right  to  expect  f excepting  io-dis- 

cover  directly  connecting  links  between  them.. but  only  be- 


480 


RECA  PTTULA  TTOK. 


tHoeu  °ac]l  and  SQme  extinct  and  supplanted  form.  Evmi 
on  a  wide  area,  winch  has  during  along  period  remained 

ofhfe  p?118'  and  °f  WKiich* the  climatic  and  other  conditions 
fi  i..  .?i  l  vUAge  msenslbI.y '1  proceeding  from  a  district  oc¬ 
cupied  by  one  species  into  another  district  occupied  bv  a 
closely  allied  species,  we  have  no  just  right  to  expect  often 
to  find  intermediate  varieties  in  the  intermediate  zones  For 
we  have  reason  to  believe  that  only  a  few  species  of  a  genus 

exrincJlde!?°l  Change;  th®  0ther  sPecies  becoming  utterly 
extinct  and  leaving  no  modified  progeny.  Of  the  species 

winch  do  change,  only  a  few  within  the  same  count™ 

effected at  T  h  ““i  ‘T5  and,  a11  modifications  are  slowly 
effected.  I  have  also  shown  that  the  intermediate  varieties 

iuld  «  a\  fil',St  eXi8te,d  in  the  intermediate  zones 
would  be  liable  to  be  supplanted  by  the  allied  forms  on 

ei  ler  hand;  for  the  latter,  from  existing  in  greater  num¬ 
bers  would  generally  be  modified  and  improved  at  a 
(pucker  rate  than  the  intermediate  varieties,  which  existed 

he  I*'  nUmber?;  80  that  the  intermediate  varieties  would 
in  the  long  run,  besuppUnted  and  exterminated. 

On  this  doctrine  of  the  extermination  of  an  infinitude  of 
r  nceung  lmks,  between  the  living  and  extinct  inhabi¬ 
tants  of  the  vvorld,  and  at  each  successive  period  be- 
ween  the  extinct  and  still  older  species,  why  is  not 
e'eiy  geological  formation  charged  with  such  links?  Whv 
does  not  every  collection  of  fossil  remains  afford  plain  evi- 
dence  of  the  gradation  and  mutation  of  the  forms  of  life? 
Although  geological  research  has  undoubtedly  revealed  the 
m  m®1  exlstence  of  many  links,  bringing  numerous  forms 
ife  much  closer  together,  it  does  not  yield  the  infinitely 
many  fine  gradations  between  past  and  present  species  ri- 
qmred  on  the  theory,  and  this  is  the  most  obvious  of  the 
many  objections  which  may  be  urged  against  it  Whv 
again,  do  whole  groups  of  allied  species  appear’  though 
this  appearance  is  often  false,  to  have  come  in  suddenly  on 
t  e  successive  geological  stages?  Although  we  now  know 
that  organic  beings  appeared  on  this  globe,  at  a  period  in¬ 
calculably  remote,  long  before  the  lowest  bed  of  Pthe  Cam¬ 
brian  system  was  deposited,  why  do  we  not  find  beneath 
this  system  great  piles  of  strata  stored  with  the  remains  of 
he  progenitors  of  the  Cambrian  fossils?  For  on  the 
tlieoiy,  such  strata  must  somewhere  have  been  deposited  at 


REGAPITULA  TIOJS.  481 

these  ancient  and  utterly  unknown  epochs  of  the  world’s 
history. 

I  can  answer  these  questions  and  objections  only  on  the 
supposition  that  the  geological  record  is  far  more  imperfect 
than  most  geologists  believe.  The  number  of  specimens  in 
all  our  museums  is  absolutely  as  nothing  compared  with 
the  countless  generations  of  countless  species  which  have 
certainly  existed.  The  parent  form  of  any  two  or  more 
species  would  not  be  in  all  its  characters  directly  interme¬ 
diate  between  its  modified  offspring,  any  more  than  the 
rock-pigeon  is  directly  intermediate  in  crop  and  tail  be¬ 
tween  its  descendants,  the  pouter  and  fantail  pigeons. 
We  should  not  be  able  to  recognize  a  species  as  the  parent 
of  another  and  modified  species,  if  we  were  to  examinine 
the  two  ever  so  closely,  unless  we  possessed  most  of  the 
intermediate  links;  and  owing  to  the  imperfection  of  the 
geological  record,  we  have  no  just  right  to  expect  to  find 
so  many  links.  If  two  or  three,  or  even  more  linking 
forms  were  discovered,  they  would  simply  be  ranked  by 
many  naturalists  as  so  many  new  species,  more  especially  if 
found  in  different  geological  substages,  let  their  dif¬ 
ferences  be  ever  so  slight.  Numerous  existing  doubtful 
forms  could  be  named  which  are  probably  varieties;  but 
who  will  pretend  that  in  future  ages  so  many  fossil  links 
will  be  discovered,  that  naturalists  will  be  able  to  decide 
whether  or  not  these  doubtful  forms  ought  to  be  called 
varieties?  Only  a  small  portion  of  the  world  has  been  geo¬ 
logically  explored.  Only  organic  beings  of  certain  classes 
can  be  preserved  in  a  fossil  condition,  at  least  in  any  great 
number.  Many  species  when  once  formed  never  undergo 
any  further  change  but  become  extinct  without  leaving 
modified  descendants;  and  the  periods  during  which  spe¬ 
cies  have  undergone  modification,  though  long  as  meas¬ 
ured  by  years,  have  probably  been  short  in  comparison 
with  the  periods  during  which  they  retained  the  same 
form.  It  is  the  dominant  and  widely  ranging  species 
which  vary  most  frequently  and  vary  most,  and  varieties 
are  often  at  first  local — both  causes  rendering  the  discov¬ 
ery  of  intermediate  links  in  any  one  formation  less  likely. 
Local  varieties  will  not  spread  into  other  and  distant 
regions  until  they  are  considerably  modified  and  improved; 
and  when  they  hive  spread,  and  are  discovered  in  a  geolog- 


482 


REG  A  PI  TULA  TION. 


ical  formation,  they  appear  as  if  suddenly  created  there, 
and  will  he  simply  classed  as  new  species.  Most  forma¬ 
tions  have  been  intermittent  in  their  accumulation,  and 
their  duration  has  probably  been  shorter  than  the  average 
duration  of  specific  forms.  Successive  formations  are  Tn 
most  cases  separated  from  each  other  by  blank  intervals  of 
time  of  great  length,  for  fossiliferons  formations  thick 
enough  to  resist  future  degradation  can,  as  a  general  rule, 
be  accumulated  only  where  much  sediment  is  deposited  on 
the  subsiding  bed  of  the  sea.  During  the  alternate  periods  of 
elevation  and  of  stationary  level  the  record  will  generally 
be  blank.  During  these  latter  periods  there  will  probably 
be  more  variability  in  the  forms  of  life;  during  periods  of 
subsidence,  more  extinction. 

.  With  res]Dect  to  the  absence  of  strata  rich  in  fossils  be¬ 
neath  the  Cambrian  formation,  I  can  recur  only  to  the 
hypothesis  given  in  the  tenth  chapter;  namely,  that  though 
our  continents  and  oceans  have  endured  for  an  enormous 
period  in  nearly  their  present  relative  positions,  we  have 
no  reason  to  assume  that  this  has  always  been  the  case; 
consequently  formations  much  older  than  any  now  known 
may  lie  buried  beneath  the  great  cceans.  With  respect  to 
the  lapse  of  time  not  having  been  sufficient  since  our  planet 
was  consolidated  for  the  assumed  amount  of  organic  change, 
and  this  objection,  as  urged  by  Sir  William  Thompson, & is 
probably  one  of  the  gravest  as  yet  advanced,  I  can  only 
say,  firstly,  that  we  do  not  know  at  what  rate  species  change, 
as  measured  by  years,  and  secondly,  that  many  philoso¬ 
phers  are  not  as  yet  willing  to  admit  that  we  know  enough 
of  the  constitution  of  the  universe  and  of  the  interior  of 
our  globe  to  speculate  with  safety  on  its  past  duration. 

That  the  geological  record  is  imperfect  all  will  admit; 
but  that  it  is  imperfect  to  the  degree  required  by  our 
theory,  few  will  be  inclined  to  admit.  If  we  look  to  long 
enough  intervals  of  time,  geology  plainly  declares  that 
species  have  all  changed;  and  they  have  changed  in  the 
manner  required  by  the  theory,  for  they  have  changed 
slowly  and  in  a  graduated  manner.  We  clearly  see  this  in 
the  fossil  remains  from  consecutive  formations  invariably 
being  much  more  closely  related  to  each  other  than  are  the 
fossils  from  widely  separated  formations. 

Such  is  the  sum  of  the  several  chief  objections  and 


RECAPITULA  TION . 


483 


difficulties  which  may  be  justly  urged  against  the  theory; 
and  I  have  now  briefly  recapitulated  the  answers  and  ex¬ 
planations  which,  as  far  as  I  can  see,  may  be  given. 

I  have  felt  these  difficulties  far  too  heavily  during  many 
years  to  doubt  their  weight.  But  it  deserves  especial  notice 
that  the  more  important  objections  relate  to  questions  on 
which  we  are  confessedly  ignorant;  nor  do  we  know  how 
ignorant  we  are.  We  do , not  know  all  the  possible  transi¬ 
tional  gradations  between  the  simplest  and  the  mosUper- 
fect  organs;  it  cannot  be  pretended  that  we  know  all  the 
varied  means  of  Distribution  during  the  long  lapse  of 
years,  or  that  we  know  how  imperfect  is  the  Geological 
Record.  Serious  as  these  several  objections  are,  in  my 
judgment  they  are  by  no  means  sufficient  to  overthrow  the 
theory  of  descent  with  subsequent  modification. 

Now  let  us  turn  to  the  other  side  of  the  argument. 
Under  domestication  we  see  much  variability,  caused,  or  at 
least  excited,  by  changed  conditions  of  life;  but  often  in  so 
obscure  a  manner,  that  we  are  tempted  to  consider  the  varia¬ 
tions  as  spontaneous.  Variability  is  governed  by  many  com-  \ 
plex  laws,  by  correlated  growth,  compensation,  the  increased 
use  and  disuse  of  parts,  and  the  definite  action  of  the  sur-  l 
rounding  conditions.  There  is  much  difficulty  in  ascer¬ 
taining  how  largely  our  domestic  productions  have  been 
modified;  but  we  may  safely  infer  that  the  amount  has  ‘ 
been  large,  and  that  modifications  can  be  inherited  for  long 
periods.  As  long  as  the  conditions  of  life  remain  the  same, 
we  have  reason  to  believe  that  a  modification,  which  has 
already  been  inherited  for  many  generations,  may  continue 
to  be  inherited  for  an  almost  infinite  number  of  generations. 
On  the  other  hand  we  have  evidence  that  variability,  when 
it  has  once  come  into  play,  does  not  cease  under  domesti¬ 
cation  for  a  very  long  period  ;  nor  do  we  know  that  it 
ever  ceases,  for  new  varieties  are  still  occasionally  pro¬ 
duced  by  our  oldest  domesticated  productions.  ^ 

Variability  is  not  actually  caused  by  man  ;^ie  only 
unintentionally  exposes  organic  beings  to  new  conditions 
of  life  and  then  nature  acts  on  the  organization  and  causes 
it  to  vary.  But  man  can  and  does  select  the  variations 
given  to  him  by  nature,  and  thus  accumulates  them  in  any 
desired  manner.  He  thus  adapts  animals  and  plants  for 


484 


RECAPITULA  TION. 


his  own  benefit  or  pleasure.  He  may  do  this  methodically, 
or  he  may  do  it  unconsciously  by  preserving  the  individ¬ 
uals  most  useful  or  pleasing  to  him  without  any  intention 
of  altering  the  breed.  It  is  certain  that  he  can  largely 
influence  the  character  of  a  breed  by  selecting,  in  each  suc¬ 
cessive  generation,  individual  differences  so  slight  as  to  be 
inappreciable  except  by  an  educated  eye.  This  unconscious 
process  of  selection  has  been  the  great  agency  in  the  for¬ 
mation  of  the  most  distinct  and  useful  domestic  breeds. 
That  many  breeds  produced  by  man  have  to  a  large  extent 
the  character  of  natural  species,  is  shown  by  the  inextri¬ 
cable  doubts  whether  many  of  them  are  varieties  or  aborig¬ 
inally  distinct  species. 

There  is  no  reason  why  the  principles  which  have  acted 
so  efficiently  under  domestication  should  not  have  acted 
under  nature.  In  the  survival  of  favored  individuals  and 
races,  during  the  constantly  recurrent  Struggle  for  Exist¬ 
ence,  we  see  a  powerful  and  ever-acting  form  of  Selection. 
The  struggle  for  existence  inevitably  follows  from  the  high 
geometrical  ratio  of  increase  which  is  common  to  all 
organic  beings.  This  high  rate  of  increase  is  proved  by 
calculation — by  the  rapid  increase  of  many  animals  and 
plants  during  a  succession  of  peculiar  seasons,  and  when 
naturalized  in  new  countries.  More  individuals  are  born 
than  can  possibly  survive.  A  grain  in  the  balance  may 
determine  which  individuals  shall  live  and  which  shall  die 
— which  variety  or  species  shall  increase  in  number,  and 
which  shall  decrease;  or  finally  become  extinct.  As  the 
individuals  of  the  same  species  come  in  all  respects  into 
the  closest  competition  with  each  other,  the  struggle  will 
generally  be  most  severe  between  them  ;  it  will  be  almost 
equally  severe  between  the  varieties  of  the  same  species, 
and  next  in  severity  between  the  species  of  the  same  genus. 
On  the  other  hand  the  struggle  will  often  be  severe 
between  beings  remote  in  the  scale  of  nature.  The 
slightest  advantage  in  certain  individuals,  at  any  age  or 
during  any  season,  over  those  with  which  they  come  into 
competition,  or  better  adaptation  in  however  slight  a 
degree  to  the  surrounding  physical  conditions,  will,  in  the 
long  run,  turn  the  balance. 

With  animals  having  separated  sexes,  there  will  be  in 
most  cases  a  struggle  between  the  males  for  the  possession 


RECAPITULA  TION. 


485 


of  the  females.  The  most  vigorous  males,  or  those  which 
have  most  successfully  struggled  with  their  conditions  of 
life,  will  generally  leave  most  progeny.  But  success  will 
often  depend  on  the  males  having  special  weapons  or  means 
of  defense  or  charms ;  and  a  slight  advantage  will  lead 
to  victory. 

As  geology  plainly  proclaims  that  each  land  has  under¬ 
gone  great  physical  changes,  we  might  have  expected  to 
find  that  organic  beings  have  varied  under  nature,  in  the 
same  way  as  they  have  varied  under  domestication.  And 
if  there  has  been  any  variability  under  nature,  it  would  be 
an  unaccountable  fact  if  natural  selection  had  not  come 
into  play.  It  has  often  been  asserted,  but  the  assertion  is 
incapable  of  proof,  that  the  amount  of  variation  under 
nature  is  a  strictly  limited  quantity.  Man,  though  acting 
on  external  characters  alone  and  often  capriciously,  can 
produce  within  a  short  period  a  great  result  by  adding  up 
mere  individual  differences  in  his  domestic  productions; 
and  every  one  admits  that  species  present  individual  differ¬ 
ences.  But,  beside  such  differences,  all  naturalists  admit 
that  natural  varieties  exist,  which  are  considered 
sufficiently  distinct  to  be  worthy  of  record  in  systematic 
works.  No  one  has  drawn  any  clear  distinction  between 
individual  differences  and  slight  varieties;  or  between  more 
plainly  marked  varieties  and  subspecies  and  species.  On 
separate  continents,  and  on  different  parts  of  the  same  con¬ 
tinent,  when  divided  by  barriers  of  any  kind,  and  on  outlying 
islands,  what  a  multitude  of  forms  exist,  which  some 
experienced  naturalists  rank  as  varieties,  others  as  geo¬ 
graphical  races  or  subspecies,  and  others  as  distinct, 
though  closely  allied  species! 

If,  then,  animals  and  plants  do  vary,  let  it  be  ever  so 
slightly  or  slowly,  why  should  not  variations  or  individual 
differences,  which  are  in  any  way  beneficial,  be  preserved 
and  accumulated  through  natural  selection,  or  the  survival  of 
the  fittest?  If  man  can  by  patience  select  variations  useful 
to  him,  why,  under  changing  and  complex  conditions  of 
life,  should  not  variations  useful  to  nature's  living  products 
often  arise,  and  be  preserved  or  selected?  What  limit  can 
be  put  to  this  power,  acting  during  long  ages  and  rigidly 
scrutinizing  the  whole  constitution,  structure  and  habits 
of  each  creature,  favoring  the  good  and  rejecting  the  bad? 


486 


RECAPITULA  TION. 


I  can  see  no  limit  to  this  power,  in  slowly  and  beautifully 
adapting  each  form  to  the  most  complex  relations  of  life. 
4  he  theory  of  natural  selection,  even  if  we  look  no  further 
than  this,  seems  to  be  in  the  highest  degree  probable.  I 
have  already  recapitulated,  as  fairly  as  I  could,  the  opposed 
difficulties  and  objections:  now  let  us  turn  to  the  special 
facts  and  arguments  in  favor  of  the  theory. 

On  the  view  that  species  are  only  strongly  marked  and 
permanent  varieties,  and  that  each  species  first  existed  as  a 
variety,  we  can  see  why  it  is  that  no  line  of  demarcation 
can  be  drawn  between  species,  commonly  supposed  to  have 
been  produced  hy  special  acts  of  creation,  and  varieties 
which  are  acknowledged  to  have  been  produced  by  second¬ 
ary  laws.  On  this  same  view  we  can  understand  how  it 
is  that  in  a  region  where  many  species  of  a  genus  have  been 
produced,  and  where  they  now  flourish,  these  same  species 
should  present  many  varieties;  for  where  the  manufactory 
of  species  has  been  active,  we  might  expect,  as  a  general 
rule,  to  find  it  still  in  action;  and  this  is  the  case  if  varie¬ 
ties  be  incipient  species.  Moreover,  the  species  of  the 
larger  genera,  which  afford  the  greater  number  of  varieties 
or  incipient  species,  retain  to  a  certain  degree  the  character 
of  varieties;,  for  they  differ  from  each  other  by  a  less 
amount  of  difference  than  do  the  species  of  smaller  genera. 
The  closely  allied  species  also  of  a  larger  genera  apparently 
have  restricted  ranges,  and  in  their  affinities  they  are 
clustered  in  little  groups  round  other  species— in  both 
respects  resembling  varieties.  These  are  strange  relations 
on  the  view  that  each  species  was  independently  created, 
but  are  intelligible  if  each  existed  first  as  a  variety. 

As  each  species  tends  by  its  geometrical  rate  of  repro¬ 
duction  to  increase  inordinately  in  number;  and  as  the 
modified  descendants  of  each  species  will  be  enabled  to 
increase  by  as  much  as  they  become  more  diversified  in 
habits  and  structure,  so  as  to  be  able  to  seize  on  many  and 
widely  different  places  in  the  economy  of  nature,  there 
will  be  a  constant  tendency  in  natural  selection  to  preserve 
the. most  divergent  offspring  of  any  one  species.  Hence, 
during  a  long-continued  course  of  modification,  the 
slight  differences  characteristic  of  varieties  of  the  same 
species,  tend  to  be  augmented  into  the  greater  differences 


R  EC  A  PTTUL  A  TION. 


487 


characteristic  of  the  species  of  the  same  genus.  New  and 
improved  varieties  will  inevitably  supplant  and  exterminate 
the  older,  less  improved,  and  intermediate  varieties;  and 
thus  species  are  rendered  to  a  large  extent  defined  and  dis- 
’  tinct  objects.  Dominant  species  belonging  to  the  larger 
groups  within  each  class  tend  to  give  birth  to  new  and 
dominant  forms;  so  that  each  large  group  tends  to  become 
still  larger,  and  at  the  same  time  more  divergent  in  character. 
But  as  all  groups  cannot  thus  go  on  increasing  in  size,  for 
the  world  would  not  hold  them,  the  more  dominant  groups 
beat  the  less  dominant.  This  tendency  in  the  large  groups 
to  go  on  increasing  in  size  and  diverging  in  character, 
together  with  the  inevitable  contingency  of  much  extinc¬ 
tion,  explains  the  arrangement  of  all  the  forms  of  life  in 
groups  subordinate  to  groups,  all  within  a  few  great  classes, 
which  has  prevailed  throughout  all  time.  This  grand  fact 
of  the  grouping  of  all  organic  beings  under  what  is  called 
the  Natural  System,  is  utterly  inexplicable  on  the  theory 
of  creation. 

As  natural  selection  acts  solely  by  accumulating  slight, 
successive,  favorable  variations,  it  can  produce  no  great  or 
sudden  modifications;  it  can  act  only  by  short  and  slow 
steps.  Hence,  the  canon  of  “  Natura  non  facit  saltum,” 
which  every  fresh  addition  to  our  knowledge  tends  to  con¬ 
firm,  is  on  this  theory  intelligible.  We  can  see  why 
throughout  nature  the  same  general  end  is  gained  by  an 
almost  infinite  diversity  of  means,  for  every  peculiarity 
when  once  acquired  is  long  inherited,  and  structures 
already  modified  in  many  different  ways  have  to  be  adapted 
for  the  same  general  purpose.  We  can,  in  short,  see  wh}^ 
nature  is  prodigal  in  variety,  though  niggard  in  innovation. 
But  why  this  should  be  a  law  of  nature  if  each  species  has 
been  independently  created  no  man  can  explain. 

Many  other  facts  are,  as  it  seems  to  me,  explicable  on 
this  theory.  How  strange  it  is  that  a  bird,  under  the  form 
of  a  woodpecker,  should  prey  on  insects  on  the  ground; 
that  upland  geese,  which  rarely  or  never  swim,  would 
possess  webbed  feet;  that  a  thrush-like  bird  should  dive 
and  feed  on  sub-aquatic  insects;  and  that  a  petrel  should 
have  the  habits  and  structure  fitting  it  for  the  life  of  an 
qji IrT  and  so  in  endless  other  cases.  But  on  the  view  of 
each  species  constantly  trying  to  increase  in  number,  with 


488 


RECA  PITITLA  TION. 


natural  selection  always  ready  to  adapt  the  slowly  varying 
descendants  of  each  to  any  unoccupied  or  ill-occupied  place 
m  natuie,  these  facts  cease  to  be  strange,  or  migfht  even 
have  been  anticipated. 

We  can  to  a  certain  extent  understand  how  it  is  that 
there  is  so  much  beauty  throughout  nature;  for  this  may 
be  largely  attributed  to  the  agency  of  selection.  That 
beauty,  according  to  our  sense  of  it,  is  not  universal,  must 
be  admitted  by  every  one  who  will  look  at  some  venomous 
snakes,  at  some  fishes,  and  at  certain  hideous  bats  with  a 
distorted  resemblance  to  the  human  face.  Sexual  selection 
has  given  the  most  brilliant  colors,  elegant  patterns,  and 
other  ornaments  to  the  males,  and  sometimes  to  both  sexes 
oi  many  birds,  butterflies  and  other  animals.  With  birds 
it  has  often  rendered  the  voice  of  the  male  musical  to  the 
temale,  as  well  as  to  our  ears.  Flowers  and  fruit  have 
been  rendered  conspicuous  by  brilliant  colors  in  contrast 
with  the  green  foliage,  in  order  that  the  flowers  may  be 
easily  seen,  visited  and  fertilized  by  insects,  and  the  seeds 
disseminated  by  birds.  How  it  comes  that  certain  colors 
sounds  and  forms  should  give  pleasure  to  man  and  the 
lower  animals,  that  is,  how  the  sense  of  beauty  in  its 
simplest  form  was  first  acquired,  we  do  not  know  any 

more  than  how  certain  odors  and  flavors  were  first  rendered 
agreeable. 

.  As  natufal  selection  acts  by  competition,  it  adapts  and 
lmpioves  the  inhabitants  of  each  country  only  in  relation 
to  their  co-inhabitants;  so  that  we  need  feel  no  surprise  at 
the  species  of  any  one  country,  although  on  the  ordinary 
view  supposed  to  have  been  created  and  specially  adapted 
tor  that  country,  being  beaten  and  supplanted  by  the 
naturalized  productions  from  another  land.  Nor  ouo-ht 
we  to  marvel  if  all  the  contrivances  in  nature  be  notfas 
tar  ns  we  can  judge,  absolutely  perfect,  as  in  the  case  even 
ot  the  human  eye;  or  if  some  of  them  be  abhorrent  to  our 
ideas  of  fitness.  We  need  not  marvel  at  the  sting  of  the 
bee  when  used  against  an  enemy,  causing  the  bee's  own 
death,  at  drones  being  produced  in  such  great  numbers 
foi  one  single  act,  and  being  then  slaughtered  by  their 
sterile  sisters;  at  the  astonishing  waste  of  pollen  by  our 
fir-trees;  at  the  instinctive  hatred  of  the  queen-bee  for  her 
own  fertile  daughters;  at  ichneumonidse  feeding  within  the 


RECAPITULATION. 


489 


living  bodies  of  caterpillars;  or  at  other  such  cases.  The 
wonder,  indeed,  is,  on  the  theory  of  natural  selection,  that 
more  cases  of  the  want  of  absolute  perfection  have  not  been 
detect  3d. 

The  complex  and  little  known  laws  governing  the  pro- 
duction  of  varieties  are  the  same,  as  far  as  we  can  judge, 
with  the  laws  which  have  governed  the  production  of  dis¬ 
tinct  species.  In  both  cases  physical  conditions  seem  to 
have  produced  some  direct  and  definite  effect,  but  how 
much  we  cannot  say.  Thus,  when  varieties  enter  any  new 
station,  they  occasionally  assume  some  of  the  characters 
proper  to  the  species  of  that  station.  With  both  varieties 
and  species,  use  and  disuse  seem  to  have  produced  a  con¬ 
siderable  effect;  for  it  is  impossible  to  resist  this  conclusion 
when  we  look,  for  instance,  at  the  logger-headed  duck, 
which  has  wings  incapable  of  flight,  in  nearly  the  same 
condition  as  in  the  domestic  duck;  or  when  we  look  at 
the  burrowing  tucu-tucu,  which  is  occasionally  blind,  and 
then  at  certain  moles,  which  are  habitually  blind  and  have 
their  eyes  covered  with  skin;  or  when  we  look  at  the  blind 
animals  inhabiting  the  dark  caves  of  America  and  Europe. 
With  varieties  and  species,  correlated  variation  seems  to 
have  played  an  important  part,  so  that  when  one  part  has 
been  modified  other  parts  have  been  necessarially  modified. 
With  both  varieties  and  species,  reversions  to  long-lost 
characters  occasionally  occur.  How  inexplicable  on  the 
theory  of  creation  is  the  occasional  appearance  of  stripes 
on  the  shoulders  and  legs  of  the  several  species  of  the 
horse-genus  and  of  their  hybrids!  How  simply  is  this 
fact  explained  if  we  believe  that  these  species  are  all  de¬ 
scended  from  a  striped  progenitor,  in  the  same  manner  as 
the  several  domestic  breeds  of  the  pigeon  are  descended 
from  the  blue  and  barred  rock-pigeon! 

On  the  ordinary  view  of  each  species  having  been  inde¬ 
pendently  created,  why  should  specific  characters,  or  those 
by  which  the  species  of  the  same  genus  differ  from  each 
other,  be  more  variable  than  generic  characters  in  which 
they  all  agree?  Why,  for  instance,  should  the  color  of  a 
flower  be  more  likely  to  vary  in  any  one  species  of  a  genus, 
if  the  other  species  possess  differently  colored  flowers,  than 
if  all  possessed  the  same  colored  flowers?  If  species  are 
only  well-marked  varieties,  of  which  the  characters  have 


490 


RECAP  IT  IT  LA  TlON. 


become  in  a  high  degree  permanent,  we  can  understand 
this  fact;  for  they  have  already  varied  since  they  branched 
off  from  a  common  progenitor  in  certain  characters,  by 
which  they  have  come  to  be  specifically  distinct  from  each 
other;  therefore  these  same  characters  would  be  more 
likely  again  to  vary  than  the  generic  characters  which  have 
been  inherited  without  change  for  an  immense  period. 
It  is  inexplicable  on  the  theory  of  creation  why  a  part  de¬ 
veloped  in  a  very  unusual  manner  in  one  species  alone  of  a 
genus,  and  therefore,  as  we  may  naturally  infer,  of  great 
importance  to  that  species,  should  be  eminently  liable  to 
variation;  but,  on  our  view,  this  part  has  undergone, 
since  the  several  species  branched  off  from  a  common  pro¬ 
genitor,  an  unusual  amount  of  variability  and  modification, 
and  therefore  we  might  expect  the  part  generally  to  be 
still  variable.  But  a  part  may  be  developed  in  the  most 
unusual  manner,  like  the  wing  of  a  bat,  and  yet  not  be 
more  variable  than  any  other  structure,  if  the  part  be  com¬ 
mon  to  many  subordinate  forms,  that  is,  if  it  has  been  in¬ 
herited  for  a  very  long  period;  for  in  this  case  it  will  have 
been  rendered  constant  by  long-continued  natural  selection. 

Glancing  at  instincts,  marvelous  as  some  are,  they  offer 
no  greater  difficulty  than  do  corporeal  structures  on  the 
theory  of  the  natural  selection  of  successive,  slight,  but 
profitable  modifications.  We  can  thus  understand  why 
nature  moves  by  graduated  steps  in  endowing  different 
animals  of  the  same  cla  ss  with  their  several  instincts.  I 
have  attempted  to  show  how  much  light  the  principle  of 
gradation  throws  on  the  admirable  architectural  powers  of 
the  hive-bee.  Habit  no  doubt  often  comes  into  play  in 
modifying  instincts;  but  it  certainly  is  not  indispensable, 
as  we  see  in  the  case  of  neuter  insects,  which  leave  no 
progeny  to  inherit  the  effects  of  long-continued  habit. 
On  the  view  of  all  the  species  of  the  same  genus  having 
descended  from  a  common  parent,  and  having  inherited 
much  in  common,  we  can  understand  how  it  is  that  allied 
species,  when  placed  under  widely  different  conditions  of 
life,  yet  follow  nearly  the  same  instincts;  why  the  thrushes 
of  tropical  and  temperate  South  America,  for  instance, 
line  their  nests  with  mud  like  our  British  species.  On  the 
view  of  instincts  having  been  slowly  acquired  through 
natural  selection,  we  need  not  marvel  at  some  instincts 


RECAP  ITU  LA  TION, 


491 


being  not  perfect  and  liable  to  mistakes,  and  at  many 
instincts  causing  other  animals  to  suffer. 

If  species  be  only  well-marked  and  permanent  varieties, 
we  can  at  once  see  why  their  crossed  offspring  should 
follow  the  same  complex  laws  in  their  degrees  and  kinds  of 
resemblance  to  their  parents — in  being  absorbed  into  each 
other  by  successive  crosses,  and  in  other  such  points — as  do 
the  crossed  offspring  of  acknowledged  varieties.  This 
similarity  would  be  a  strange  fact,  if  species  had  been  in¬ 
dependently  created  and  varieties  had  been  produced 
through  secondary  laws. 

If  we  admit  that  the  geological  record  is  imperfect  to  an 
extreme  degree,  then  the  facts,  which  the  record  does  give, 
strongly  support  the  theory  of  descent  with  modification. 
New  species  have  come  on  the  stage  slowly  and  at  succes¬ 
sive  intervals;  and  the  amount  of  change  after  equal 
intervals  of  time,  is  widely  different  in  different  groups. 
The  extinction  of  species  and  of  whole  groups  of  species, 
which  has  played  so  conspicuous  a  part  in  the  history  of 
the  organic  world,  almost  inevitably  follows  from  the  prin¬ 
ciple  of  natural  selection ;  for  old  forms  are  -supplanted  by 
new  and  improved  forms.  Neither  single  species  nor 
groups  of  species  reappear  when  the  chain  of  ordinary 
generation  is  once  broken.  The  gradual  diffusion  of  dom¬ 
inant  forms,  with  the  slow  modification  of  their  descend¬ 
ants,  causes  the  forms  of  life,  after  long  intervals  of  time, 
to  appear  as  if  they  had  changed  simultaneously  through¬ 
out  the  world.  The  fact  of  the  fossil  remains  of  each 
formation  being  in  some  degree  intermediate  in  character 
between  the  fossils  in  the  formations  above  and  below,  is 
simply  explained  by  their  intermediate  position  in  the 
chain  of  descent,  the  grand  fact  that  all  extinct  beings 
can  be  classed  with  all  recent  beings,  naturally  follows  from 
the  living  and  the  extinct  being  the  offspring  of  common 
parents.  As  species  have  generally  diverged  in  character 
during  their  long  course  of  descent  and  modification,  we 
can  understand  why  it  is  that  the  more  ancient  forms,  or 
early  progenitors  of  each  group,  so  often  occupy  a  position 
in  some  degree  intermediate  between  existing  groups. 
Recent  forms  are  generally  looked  upon  as  being,  on  the 
whole,  higher  in  the  scale  of  organization  than  ancient 
forms;  and  they  must  be  higher,  in  so  far  as  the  later  and 


m 


RECAriTVLA  TION. 


more  improved  forms  have  conquered  the  older  and  less 
improved  forms  in  the  struggle  for  life;  they  have  also 
generally  had  their  organs  more  specialized  for  different 
functions.  This  fact  is  perfectly  compatible  with  numer¬ 
ous  beings  still  retaining  simple  and  but  little  improved 
structures,  fitted  for  simple  conditions  of  life;  it  is  likewise 
compatible  with  some  forms  having  retrograded  in  organi¬ 
zation,  by  having  become  at  each  stage  of  descent  better 
fitted  for  new  and  degraded  habits  of  life.  Lastly,  the 
wonderful  law  of  the  long  endurance  of  allied  forms  on  the 
same  continent — of  marsupials  in  Australia,  of  edentata  in 
America,  and  other  such  cases — is  intelligible,  for  within 
the  same  country  the  existing  and  the  extinct  will  be 
closely  allied  by  descent. 

Looking  to  geographical  distribution,  if  we  admit  that 
there  has  been  during  the  long  course  of  ages  much  migra¬ 
tion  from  one  part  of  the  world  to  another,  owing  to 
former  climatical  and  geographical  changes  and  to  the 
many  occasional  and  unknown  means  of  dispersal,  then 
we  can  understand,  on  the  theory  of  descent  with  modi¬ 
fication,  most  of  the  great  leading  facts  in  distribution. 
We  can  see  why  there  should  be  so  striking  a  parallelism 
in  the  distribution  of  organic  beings  throughout  space,  and 
in  their  geological  succession  throughout  time;  for  in 
both  cases  the  beings  have  been  connected  by  the  bond 
of  ordinary  generation,  and  the  means  of  modification 
have  been  the  same.  We  see  the  full  meaning  of  the 
wonderful  fact,  which  has  struck  every  traveler,  namely, 
that  on  the  same  continent,  under  the  most  diverse  con¬ 
ditions,  under  heat  and  cold,  on  mountain  and  lowland, 
on  deserts  and  marshes,  most  of  the  inhabitants  within 
each  great  class  are  plainly  related;  for  they  are  the  descend¬ 
ants  of  the  same  progenitors  and  early  colonists.  On  this 
same  principle  of  former  migration,  combined  in  most 
cases  with  modification,  we  can  understand,  by  the  aid  of 
the  Glacial  period,  the  identity  of  some  few  plants,  and  the 
close  alliance  of  many  others,  on  the  most  distant  mount¬ 
ains,  and  in  the  northern  and  southern  temperate  zones; 
and  likewise  the  close  alliance  of  some  of  the  inhabitants 
of  the  sea  in  the  northern  and  southern  temperate  lati¬ 
tudes,  though  separated  by  the  whole  intertropical  ocean. 
Although  two  countries  may  nresent  physical  conditions  as 


RECAPITULA  770 N. 


493 


closely  similar  as  the  same  species  ever  require,  we  need 
feel  no  surprise  at  their  inhabitants  being  widely  different, 
if  they  have  been  for  a  long  period  completely  sundered 
from  each  other;  for  as  the  relation  of  organic  to  organ¬ 
ism  is  the  most  important  of  all  relations,  an.  as  the  two 
countries  will  have  received  colonists  at  various  periods 
and  in  different  proportions,  from  some  other  country  or 
from  each  other,  the  course  of  modification  in  the  two 
areas  will  inevitably  have  been  different. 

#  On  this  view  of  migration,  with  subsequent  modifica¬ 
tion,  we  see  why  oceanic  islands  are  inhabited  by  only  few 
species,  but  of  these,  why  many  are  peculiar  or  endemic 
forms.  We  clearly  see  why  species  belonging  to  those 
groups  of  animals  which  cannot  cross  wide  spaces  of  the 
ocean,  as  frogs  and  terrestrial  mammals,  do  not  inhabit 
oceanic  islands;  and  why,  on  the  other  hand,  new  and 
peculiar  species  of  bats,  animals  which  can  traverse  the 
ocean,  are  often  found  on  islands  far  distant  from  any  con¬ 
tinent.  Such  cases  as  the  presence  of  peculiar  species  of 
bats  on  oceanic  islands  and  the  absence  of  all  other  terres¬ 
trial  mammals,  are  facts  utterly  inexplicable  on  the  theory 
of  independent  acts  of  creation. 

The  existence  of  closely  allied  representative  species  in 
any  two  areas,  implies,  on  the  theory  of  descent  with 
modification,  that  the  same  parent-forms  formerly  inhab¬ 
ited  both  areas:  and  we  almost  invariably  find  that  wher¬ 
ever  many  closely  allied  species  inhabit  two  areas,  some 
identical  species  are  still  common  to  both.  Wherever 
many  closely  allied  yet  distinct  species  occur,  doubtful 
forms  and  varieties  belonging  to  the  same  groups  likewise 
occur.  It  is  a  rule  of  high  generality  that  the  inhabitants 
of  each  area  are  related  to  the  inhabitants  of  the  nearest 
source  whence  immigrants  might  have  been  derived.  We 
see  this  in  the  striking  relation  of  nearly  all  the  plants  and 
animals  of  the  Galapagos  Archipelago,  of  Juan  Fernandez, 
and  of  the  other  American  islands,  to  the  plants  and 
animals  of  the  neighboring  American  mainland;  and  of 
those  of  the  Cape  de  Verde  Archipelago,  and  of  the  other 
African  islands  to  the  African  mainland.  It  must  be  ad¬ 
mitted  that  these  facts  receive  no  explanation  on  the 
theory  of  creation. 

The  fact,  as  we  have  seen,  that  all  past  and  present 


494 


'RECAP  1TTJ LA  TION . 


organic  beings  can  be  arranged  within  a  few  great  classes,  in 
groups  subordinate  to  groups,  and  with  the  extinct  groups 
often  falling  in  between  the  recent  groups,  is  intelligible 
on  the  the  of  natural  selection  with  its  contingencies  of 
extinction  and  divergence  of  character.  On  these  same 
principles  we  see  how  it  is  that  the  mutual  affinities 
of  the  forms  within  each  class  are  so  complex  and 
circuitous.  We  see  why  certain  characters  are  far  more 
serviceable  than  others  for  classification;  why  adaptive 
characters,  though  of  paramount  importance  to  the  beings 
are  of  hardly  any  importance  in  classification;  why  charac¬ 
ters  derived  from  rudimentary  parts,  though  of  no  service 
to  the  beings,  are  often  of  high  classifieatory  value;  and 
why  embryological  characters  are  often  the  most  valuable 
of  all.  The  real  affinities  of  all  organic  beings,  in  contra¬ 
distinction  to  their  adaptive  resemblances,  are  due  to  inher¬ 
itance  or  community  of  descent.  The  Natural  System  is  a 
genealogical  arrangement,  with  the  acquired  grades  of  dif¬ 
ference,  marked  by  the  terms,  varieties,  species,  genera, 
families,  etc.;  and  we  have  to  discover  the  lines  of  descent 
by  the  most  permanent  characters,  whatever  they  may  be, 
and  of  however  slight  vital  importance. 

The  similar  framework  of  bones  in  the  hand  of  a  man, 
wing  of  a  bat,  fin  of  the  porpoise,  and  leg  of  the  horse — 
the  same  number  of  vertebrae  forming  the  neck  of  the 
giraffe  and  of  the  elephant — and  innumerable  other  such 
facts,  at  once  explain  themselves  on  the  theory  of  descent 
-with  slow  and  slight  successive  modifications.  The  simi¬ 
larity  of  pattern  in  the  wing  and  in  the  leg  of  a  bat,  though 
used  for  such  different  purpose — in  the  jaws  and  legs  of  a 
crab — in  the  petals,  stamens,  and  pistils  of  a  flower,  is  like¬ 
wise,  to  a  large  extent,  intelligible  on  the  view  of  the  grad¬ 
ual  modification  of  parts  or  organs,  which  were  aboriginally 
alike  in  an  early  progenitor  in  each  of  these  classes.  On 
the  principle  of  successive  variations  not  always  superven¬ 
ing  at  an  early  age,  and  being  inherited  at  a  corresponding 
not  early  period  of  life,  we  clearly  see  why  the  embryos  ox 
mammals,  birds,  reptiles,  and  fishes  should  be  so  closely 
similar,  and  so  unlike  the  adult  forms.  We  may  cease 
marveling  at  the  embryo  of  an  air-breathing  mammal  or 
bird  having  branchial  slits  and  arteries  running  in  loops, 
like  those  of  a  fish  which  has  to  breathe  the  air  dissolved 
in  water  by  the  aid  of  well-developed  branchiae. 


CONCLUSION. 


495 


Disuse,  aided  sometimes  by  natural  selection,  will  often 
have  reduced  organs  when  rendered  useless  under  changed 
habits  or  conditions  of  life;  and  we  can  understand  on  this 
view  the  meaning  of  rudimentary  organs.  But  disuse  and 
selection  will  generally  act  on  each  creature,  when  it  has 
come  to  maturity  and  has  to  play  its  full  part  in  the  strug¬ 
gle  for  existence,  and  will  thus  have  little  power  on  an 
organ  during  early  life;  hence  the  organ  will  not  be  reduced 
or  rendered  rudimentary  at  this  early  age.  The  calf,  for 
instance,  has  inherited  teeth,  which  never  cut  through  the 
gums  of  the  upper  jaw,  from  an  early  procenitor  having 
well-developed  teeth;  and  we  may  believe,  that  the  teeth  in 
the  mature  animal  were  formerly  reduced  by  disuse,  owing 
to  the  tongue  and  palate,  or  lips,  having  become  excellently 
fitted  through  natural  selection  to  browse  without  their  aid; 
whereas  in  the  calf,  the  teeth  have  been  left  unaffected, 
and  on  the  principle  of  inheritance  at  corresponding  ages 
have  been  inherited  from  a  remote  period  to  the  present 
day.  On  the  view  of  each  organism  with  all  its  separate 
parts  having  been  specially  created,  how  utterly  inexplica¬ 
ble  is  it  that  organs  bearing  the  plain  stamp  of  inutility, 
such  as  the  teeth  in  the  embryonic  calf  or  the  shriveled 
wings  under  the  soldered  wing-covers  of  many  beetles, 
should  so  frequently  occur.  Nature  may  be  said  to  have 
taken  pains  to  reveal  her  scheme  of  modification,  by  means 
of  rudimentary  organs,  of  embryological  and  homologous 
structures,  but  we  are  too  blind  to  understand  her 
meaning. 

I  have  now  recapitulated  the  facts  and  considerations 
which  have  thoroughly  convinced  me  that  species  have  been 
modified,  during  a  long  course  of  descent.  This  has  been 
effected  chiefly  through  the  natural  selection  of  numerous 
successive,  slight,  favorable  variations  ;  aided  in  an  impor¬ 
tant  manner  by  the  inherited  effects  of  the  use  and  disuse 
of  parts;  and  in  an  unimportant  manner,  that  is,  in  relation 
to  adaptive  structures,  whether  past  or  present,  by  the 
direct  action  of  external  conditions,  and  by  variations 
which  seem  to  us  in  our  ignorance  to  arise  spontaneously. 
It  appears  that  I  formerly  underrated  the  frequency  and 
value  of  these  latter  forms  of  variation,  as  leading  to  per¬ 
manent  modifications  of  structure  independently  of  natural 
selection.  But  as  my  conclusions  have  lately  been  much 


49C 


CONCLUSION. 


misrepresented,  and  it  has  been  stated  that  I  attribute  the 
modification  of  species  exclusively  to  natural  selection,  I 
may  be  permitted  to  remark  that  in  the  first  edition  of  this 
work,  and  subsequently,  I  placed  in  a  most  conspicuous 
position — namely,  at  the  close  of  the  Introduction — the 
following  words  :  “  I  am  convinced  that  natural  selection 
has  been  the  main  but  not  the  exclusive  means  of  modi- 
fication.  I  his  has  been  of  no  avail.  Great  is  the  power 
of  steady  misrepresentation  ;  but  the  history  of  science 
shows  that  fortunately  this  power  does  not  long  endure. 

It  can  hardly  be  supposed  that  a  false  theory  would 
explain,  in  so  satisfactory  a  manner  as  does  the  theory 
of  natural  selection,  the  several  large  classes  of  facts  above 
specified.  It  has  recently  been  objected  that  this  is  an 
unsafe  method  of  arguing;  but  it  is  a  method  used  in 
judging  of  the  common  events  of  life,  and  has  often  been 
used  by  the  greatest  natural  philosophers.  The  undulatory 
theory  of  light  has  thus  been  arrived  at ;  and  the  belief  iu 
the  revolution  of  the  earth  on  its  own  axis  was  until  lately 
supported  by  hardly  any  direct  evidence.  It  is  no  valid 
objection  that  science  as  yet  throws  no  light  on  the  far 
higher  problem  of  the  essence  or  origin  of  life.  Who  can 
explain  what  is  the  essence  of  the  attraction  of  gravity  ? 
No  one  now  objects  to  following  out  the  results  consequent 
on  this  unknown  element  of  attraction ;  notwithstanding 
that  Leibnitz  formerly  accused  Newton  of  introducing 
“  occult  qualities  and  miracles  into  philosophy.” 

I  see  no  good  reasons  why  the  views  given  in  this  volume 
should  shock  the  religious  feelings  of  any  one.  It  is  satis¬ 
factory,  as  showing  how  transient  such  impressions  are,  to 
remember  that  the  greatest  discovery  ever  made  by  man, 
namely,  the  law  of  the  attraction  of  gravity,  was  also 
attacked  by  Leibnitz,  “as  subversive  of  natural,  and  infer- 
entially  of  revealed,  religion.”  A  celebrated  author  and 
divine  has  written  to  me  that  “  he  has  gradually  learned  to 
see  that  it  is  just  as  noble  a  conception  of  the  Deity  to 
believe  that  He  created  a  few  original  forms  capable  of 
self-develop merit  into  other  and  needful  forms,  as  to 
believe  that  He  required  a  fresh  act  of  creation  to  supply 
the  voids  caused  by  the  action  of  His  laws.” 

Why,  it  may  be  asked,  until  recently  did  nearly  all  the 
most  eminent  living  naturalists  and  geologists  disbelieve  iu 


CON  CL  US  TON. 


49? 


Che  mutability  of  species?  It  cannot  be  asserted  that 
organic  beings  in  a  state  of  nature  are  subject  to  no  varia¬ 
tion;  it  cannot  be  proved  that  the  amount  of  variation  in 
the  course  of  long  ages  is  a  limited  quantity;  no  clear  dis¬ 
tinction  has  been,  or  can  be,  drawn  between  species  and 
well-marked  varieties.  It  cannot  be  maintained  that^ 
species  when  intercrossed  are  invariably  sterile  and  varieties 
invariably  fertile;  or  that  sterility  is  a  special  endowment 
and  sign  of  creation.  The  belief  that  species  were  immut¬ 
able  productions  was  almost  unavoidable  as  long  as  the 
history  of  the  world  was  thought  to  be  of  short  duration; 
and  now  that  we  have  acquired  some  idea  of  the  lapse  of 
time,  we  are  too  apt  to  assume,  without  proof,  that  the 
geological  record  is  so  perfect  that  it  would  have  afforded 
ns  plain  evidence  of  the  mutation  of  species,  if  they  had 
undergone  mutation. 

But  the  chief  cause  of  our  natural  unwillingness  to  admit 
that  one  species  has  given  birth  to  other  and  distinct  species, 
is  that  we  are  always  slow  in  admitting  great  changes  of 
which  we  do  not  see  the  steps.  The  difficulty  is  the  same 
as  that  felt  by  so  many  geologists,  when  Lyell  first  insisted 
that  long  lines  of  inland  cliffs  had  been  formed,  and  great 
valleys  excavated,  by  the  agencies  which  we  still  see  at  work. 
The  mind  cannot  possibly  grasp  the  full  meaning  of  the 
term  of  even  a  million  years ;  it  cannot  add  up  and  perceive 
the  full  effects  of  many  slight  variations,  accumulated  during 
an  almost  infinite  number  of  generations. 

Although  I  am  fully  convinced  of  the  truth  of  the  views 
given  in  this  volume  under  the  form  of  an  abstract,  I  by  no 
means  expect  to  convince  experienced  naturalists  whose 
minds  are  stocked  with  a  multitude  of  facts  all  viewed,  dur¬ 
ing  a  long  course  of  years,  from  a  point  of  view  directly  op¬ 
posite  to  mine.  It  is  so  easy  to  hide  our  ignorance  under 
such  expressions  as  the  “plan  of  creation,”  “unity  of  de¬ 
sign,”  etc.,  and  to  think  that  we  give  an  explanation  when 
we  only  restate  a  fact.  Any  one  whose  disposition  leads 
him  to  attach  more  weight  to  unexplained  difficulties  than 
to  the  explanation  of  a  certain  number  of  facts  will  certainly 
reject  the  theory.  A  few  naturalists,  endowed  with  much 
flexibility  of  mind,  and  who  have  already  begun  to  doubt 
the  immutability  of  species,  may  be  influenced  by  this  vol¬ 
ume;  but  I  look  with  confidence  to  the  future,  to  young 


408 


CON  CL  USIOff. 


and  rising  naturalists,  who  will  be  able  to  view  both  sides 
of  the  question  with  impartiality.  Whoever  is  led  to  be¬ 
lieve  that  species  are  mutable  will  do  good  service  by  con* 
scientiously  expressing  his  conviction  ;  for  thus  only  can  the 
load  of  prejudice  by  which  this  subject  is  overwhelmed  be 
removed. 

Several  eminent  naturalists  have  of  late  published  their 
belief  that  a  multitude  of  reputed  species  in  each  genus  are 
not  real  species;  but  that  other  species  are  real,  that  is, 
have  been  independently  created.  This  seems  to  me  a 
strange  conclusion  to  arrive  at.  They  admit  that  a  multi¬ 
tude  of  forms,  which  till  lately  they  themselves  thought 
were  special  creations,  and  which  are  still  thus  looked  at 
by  the  majority  of  naturalists,  and  which  consequently  have 
all  the  external  characteristic  features  of  true  species — 
they  admit  that  these  have  been  produced  by  variation, 
but  they  refuse  to  extend  the  same  view  to  other  and 
slightly  different  forms.  Nevertheless,  they  do  not  pretend 
that  they  can  define,  or  even  conjecture,  which  are  the 
created  forms  of  life,  and  which  are  those  produced  by 
secondary  laws.  They  admit  variation  as  a  vera  causa  in 
one  case,  they  arbitrarily  reject  it  in  another,  without  as¬ 
signing  any  distinction  in  the  two  cases.  The  day  will 
come  when  this  will  be  given  as  a  curious  illustration  of 
the  blindness  of  preconceived  opinion.  These  authors  seem 
no  more  startled  at  a  miraculous  act  of  creation  than  at  an 
ordinary  birth.  But  do  they  really  believe  that  at 
innumerable  periods  in  the  earth’s  history  certain  ele¬ 
mental  atoms  have  been  commanded  suddenly  to  flash  into 
living  tissues?  Do  they  believe  that  at  each  supposed  act 
of  creation  one  individual  or  many  were  produced?  Were 
all  the  infinitely  numerous  kinds  of  animals  and  plants 
created  as  eggs  or  seed,  or  as  full  grown?  and  in  the  case 
of  mammals,  were  they  created  bearing  the  false  marks  of 
nourishment  from  the  mother’s  womb?  Undoubtedly  some 
of  these  same  questions  cannot  be  answered  by  those  who 
believe  in  the  appearance  or  creation  of  only  a  few  forms 
of  life,  or  of  some  one  form  alone.  It  has  been  main¬ 
tained  by  several  authors  that  it  is  as  easy  to  believe  in  the 
creation  of  a  million  beings  as  of  one;  but  Maupertuis’ 
philosophical  axiom  of  least  action  ”  leads  the  mind  more 
willingly  to  admit  the  smaller  number;  and  certainly  we 


CONCLUSION. 


499 


ought  not  to  believe  that  innumerable  beings  within  each 
great  class  have  been  created  with  plain,  but  deceptive, 
marks  of  descent  from  a  single  parent. 

As  a  record  of  a  former  state  of  things,  I  have  retained 
in  the  foregoing  paragraphs,  and  elsewhere,  several  sen¬ 
tences  which  imply  that  naturalists  believe  in  the  separate 
creation  of  each  species;  and  I  have  been  much  censured 
for  having  thus  expressed  myself.  But  undoubtedly  this 
was  the  general  belief  when  the  first  edition  of  the  present 
work  appeared.  I  formerly  spoke  to  very  many  natural¬ 
ists  on  the  subject  of  evolution,  and  never  once  met  with 
any  sympathetic  agreement.  It  is  probable  that  some  did 
then  believe  in  evolution,  but  they  were  either  silent  or  ex¬ 
pressed  themselves  so  ambiguously  that  it  was  not  easy  to 
understand  their  meaning.  Now,  things  are  wholly 
changed,  and  almost  every  naturalist  admits  the  great  prim 
ciple  of  evolution.  There  are,  however,  some  who  still 
think  that  species  have  suddenly  given  birth,  through  quite 
unexplained  means,  to  new  and  totally  different  forms. 
But,  as  I  have  attempted  to  show,  weighty  evidence  can 
be  opposed  to  the  admission  of  great  and  abrupt  modifica¬ 
tions.  Under  a  scientific  point  of  view,  and  as  leading  to 
further  investigation,  but  little  advantage  is  gained  by  be= 
lieving  that  new  forms  are  suddenly  developed  in  an  inex¬ 
plicable  manner  from  old  and  widely  different  forms,  over 
the  old  belief  in  the  creation  of  species  from  the  dust  of 
the  earth. 

It  may  be  asked  how  far  I  extend  the  doctrine  of  the 
modification  of  species.  The  question  is  difficult  to 
answer,  because  the  more  distinct  the  forms  are  which  we 
consider,  by  so  much  the  arguments  in  favor  of  com¬ 
munity  of  descent  become  fewer  in  number  and  less  ir 
force.  But  some  arguments  of  the  greatest  weight  extend 
very  far.  All  the  members  of  whole  classes  are  connected 
together  by  a  chain  of  affinities,  and  all  can  be  classed  on 
the  same  principle,  in  groups  subordinate  to  groups. 
Fossil  remains  sometimes  tend  to  fill  up  very  wide  inter¬ 
vals  between  existing  orders. 

Organs  in  a  rudimentary  condition  plainly  show  that  an 
early  progenitor  had  the  organ  in  a  fully  developed  condi¬ 
tion,  and  this  in  some  cases  implies  an  enormous  amount 
of  modification  in  the  descendants.  Throughout  whole 


500 


CONCLUSION. 


classes  various  structures  are  formed  on  the  same  pattern, 
and  at  a  very  early  age  the  embryos  closely  resemble  each 
other.  Therefore  I  cannot  doubt  that  the  theory  of  de¬ 
scent  with  modification  embraces  all  the  members  of  the 
same  great  class  or  kingdom,  I  believe  that  animals  are 
descended  from  at  most  only  four  or  five  progenitors,  and 
plants  from  an  equal  or  lesser  number. 

Analogy  would  lead  me  one  step  further,  namely,  to  the 
belief  that  all  animals  and  plants  are  descended  from  some 
one  prototype.  But  analogy  may  be  a  deceitful  guide. 
Nevertheless  all  living  things  have  much  in  common,  in 
their  chemical  composition,  their  cellular  structure,  their 
laws  of  growth,  and.  their  liability  to  injurious  influences. 
We  see  this  even  in  so  trifling  a  fact  as  that  the  same 
poison  often  similarly  alfects  plants  and  animals;  or  that 
the  poison  secreted  by  the  gall-fly  produces  monstrous 
giowths  on  the  wild  rose  or  oak  tree.  With  all  organic 
beings,  excepting  perhaps  some  of  the  very  lowest,  sexual 
reproduction  seems  to  be  essentially  similar.  With  all,  as 
far  as  is  at  present  known,  the  germinal  vesicle  is  the 
same;  so  that  all  organisms  start  from  a  common  origin,: 
If  we  look  even  to  the  two  main  divisions — namely,  to^the 
animal  and  vegetable  kingdoms — certain  low  forms  are  so 
far  intermediate  in  character  that  naturalists  have  disputed 
to  which  kingdom  they  should  be  referred.  As  Professor 
Asa  Gray  has  remarked,  “  the  spores  and  other  reproduc¬ 
tive  bodies  of  many  of  the  lower  algae  may  claim  to  have 
flist  a  characteristically  animal,  and  then  an  unequivocally 
vegetable  existence.”  Therefore,  on  the  principle  of 
natural  selection  with  divergence  of  character,  it  does  not 
seem  incredible  that,  from  some  such  low  and  intermediate 
foi m,  both  animals  and  plants  may  have  been  developed" 
and.  if  we  .admit  this,  we  must  likewise  admit  that  all  the 
oiganic  beings  which  have  ever  lived  on  this  earth  may  be 
descended  from  some  one  primordial  form.  But  this  infer¬ 
ence  is  chiefly  grounded  on  analogy,  and  it  is  immaterial 
whether  or  not  it  be  accepted.  No  doubt  it  is  possible,  as 
Mr.  G.  H.  Lewes  has  urged,  that  at  the  first  commence¬ 
ment  of  life  many  different  forms  were  evolved*  but  if  so, 
we  may  conclude  that  only  a  very  few  have  left  modified 
descendants.  Por,  as  I  have  recently  remarked  in  regard 
to  the  members  of  each  great  kingdom,  such  as  the  Verte- 


CONCLUSION. 


50  J 


brata,  Articulata,  etc.,  we  have  distinct  evidence  in  their 
embryological,  homologous,  and  rudimentary  structures, 
that  within  each  kingdom  all  the  members  are  descended 
from  a  single  progenitor. 

When  the  views  advanced  by  me  in  this  volume,  and  by 
Mr.  Wallace  or  when  analogous  views  on  the  origin  of 
species  are  generally  admitted,  we  can  dimly  foresee  that 
there  will  be  a  considerable  revolution  in  natural  history. 
Systematists  will  be  able  to  pursue  their  labors  as  at  pres¬ 
ent;  but  they  will  not  be  incessantly  haunted  by  the 
shadowy  doubt  whether  this  or  that  form  be  a  true  species. 
This,  I  feel  sure  and  I  speak  after  experience,  will  be  no 
slight  relief.  The  endless  disputes  whether  or  not  some 
fifty  species  of  British  brambles  are  good  species  will  cease. 
Systematists  will  have  only  to  decide  (not  that  this  will  be 
easy)  whether  any  form  be  sufficiently  constant  and  distinct 
from  other  forms,  to  be  capable  of  definition;  and  if  defina¬ 
ble,  whether  the  differences  be  sufficiently  important  to 
deserve  a  specific  name.  This  latter  point  will  become  a 
far  more  essential  consideration  than  it  is  at  present;  for 
differences,  however  slight,  between  any  two  forms,  if  not 
blended  by  intermediate  gradations,  are  looked  at  by  most 
naturalists  as  sufficient  to  raise  both  forms  to  the  rank  of 
species. 

Hereafter  we  shall  be  compelled  to  acknowledge  that 
the  only  distinction  between  species  and  well-marked  varie¬ 
ties  is,  that  the  latter  are  known,  or  believed  to  be  con¬ 
nected  at  the  present  day  by  intermediate  gradations, 
whereas  species  were  formerly  thus  connected.  Hence, 
without  rejecting  the  consideration  of  the  present  existence 
of  intermediate  gradations  between  any  two  forms,  we 
shall  be  led  to  weigh  more  carefully  and  to  value  higher 
the  actual  amount  of  difference  between  them.  It  is  quite 
possible  that  forms  now  generally  acknowledged  to  be 
merely  varieties  may  hereafter  be  thought  worthy  of 
specific  names;  and  in  this  case  scientific  and  common  lan¬ 
guage  will  come  into  accordance.  In  short,  we  shall  have 
to  treat  species  in  the  same  manner  as  those  naturalists 
treat  genera,  who  admit  that  genera  are  merely  artificial 
combinations  made  for  convenience*  This  mav  not  be  a 
cheering  prospect;  but  we  shall  at  least  be  freed  from  the 
vain  search  for  the  undiscovered  and  undjscoverable 
essence  of  the  term  species® 


502 


CONCLUSION. 


The  other  and  more  general  departments  of  natural  his¬ 
tory  will  rise  greatly  in  interest.  The  terms  used  by  nat¬ 
uralists,  of  affinity,  relationship,  community  of  type, 
paternity,  morphology,  adaptive  characters,  rudimentary 
and  aborted  organs,  etc.,  will  cease  to  be  metaphorical  and 
will  have  a  plain  signification.  When  we  no  longer  look 
at  an  organic  being  as  a  savage  looks  at  a  ship,  as  some¬ 
thing  wholly  beyond  his  comprehension;  when  we  regard 
every  production  of  nature  as  one  which  has  had  a  long 
history;  when  we  contemplate  every  complex  structure  and 
instinct  as  the  summing  up  of  many  contrivances,  each 
useful  to  the  possessor,  in  the  same  way  as  any  great 
mechanical  invention  is  the  summing  up  of  the  labor,  the 
experience,  the  reason,  and  even  the  blunders  of  numerous 
workmen;  when  we  thus  view  each  organic  being,  how  far 
more  interesting — I  speak  from  experience — does  the  study 
of  natural  history  become! 

A  grand  and  almost  untrodden  field  of  inquiry  will  be 
opened,  on  the  causes  and  laws  of  variation,  on  correlation, 
on  the  effects  of  use  and  disuse,  on  the  direct  action  of 
external  conditions,  and  so  forth.  The  study  of  domestic 
productions  will  rise  immensely  in  value.  A  new  variety 
raised  by  man  will  be  a  more  important  and  interesting 
subject  for  study  than  one  more  species  added  to  the  infin¬ 
itude  of  already  recorded  species.  Our  classifications  will 
come  to  be,  as  far  as  they  can  be  so  made,  genealogies; 
and  will  then  truly  give  what  may  be  called  the  plan  of 
creation.  The  rules  for  classifying  will  no  doubt  become 
simpler  when  we  have  a  definite  object  in  view.  We  pos¬ 
sess  no  pedigree  or  armorial  bearings;  and  we  have  to  dis¬ 
cover  and  trace  the  many  diverging  lines  of  descent  in  our 
natural  genealogies,  by  characters  of  any  kind  which  have 
long  been  inherited.  Rudimentary  organs  will  speak 
infallibly  with  respect  to  the  nature  of  long-lost  structures. 
Species  and  groups  of  species  which  are  called  aberrant, 
and  which  may  fancifully  be  called  living  fossils,  will  aid 
us  in  forming  a  picture  of  the  ancient  forms  of  life. 
Embryology  will  often  reveal  to  us  the  structure,  in  some 
degree  obscured,  of  the  prototypes  of  each  great  class. 

When  we  can  feel  assured  that  all  the  individuals  of  the 
same  species,  and  all  the  closely  allied  species  of  most  genera, 
have,  within  a  not  very  remote  period  descended  from  one 

N 


CONCLUSION. 


503 


parent,  and  "have  migrated  from  some  one  birth-place;  anu 
when  we  better  know  the  many  means  of  migration,  then, 
by  the  light  which  geology  now  throws,  and  will  continue 
to  throw,  on  former  changes  of  climate  and  of  the  level  of 
the  land,  we  shall  surely  be  enabled  to  trace  in  an  admir¬ 
able  manner  the  former  migrations  of  the  inhabitants  of 
the  whole  world.  Even  at  present,  by  comparing  the 
differences  between  the  inhabitants  of  the  sea  on  the 
opposite  sides  of  a  continent,  and  the  nature  of  the  various 
inhabitants  on  that  continent  in  relation  to  their  apparent 
means  of  immigration,  some  light  can  be  thrown  on  ancient 
geography. 

The  noble  science  of  geology  loses  glory  from  the  extreme 
imperfection  of  the  record.  The  crust  of  the  earth,  with 
its  imbedded  remains,  must  not  be  looked  at  as  a  well-filled 
museum,  but  as  a  poor  collection  made  at  hazard  and  at 
rare  intervals.  The  accumulation  of  each  great  fossilifer- 
ous  formation  will  be  recognized  as  having  depended  on 
an  unusual  occurrence  of  favorable  circumstances,  and  the 
blank  intervals  between  the  successive  stages  as  having 
been  of  vast  duration.  But  we  shall  be  able  to  gauge  with 
some  security  the  duration  of  these  intervals  by  a  compari¬ 
son  of  the  preceding  and  succeeding  organic  forms.  We 
must  be  cautious  in  attempting  to  correlate  as  strictly 
contemporaneous  two  formations,  which  do  not  include 
many  identical  species,  by  the  general  succession  of  the 
forms  of  life.  As  species  are  produced  and  exterminated 
by  slowly  acting  and  still  existing  causes,  and  not  by 
miraculous  acts  of  creation;  and  as  the  most  important  of 
all  causes  of  organic  change  is  one  which  is  almost  inde¬ 
pendent  of  altered  and  perhaps  suddenly  altered  physical 
conditions,  namely,  the  mutual  relation  of  organism  to 
organism — the  improvement  of  one  organism  entailing  the 
improvement  or  the  extermination  of  others;  it  follows, 
that  the  amount  of  organic  change  in  the  fossils  of  con¬ 
secutive  formations  probably  serves  as  a  fair  measure  of 
the  relative,  though  not  actual  lapse  of  time.  A  number 
of  species,  however,  keeping  in  a  body  might  remain  for  a 
long  period  unchanged,  while  within  the  same  period, 
several  of  these  species,  by  migrating  into  new  countries 
and  coming  into  competition  with  foreign  associates,  might 
become  modified;  so  that  we  must  not  overrate  the  accuracy 
of  organic  change  as  a  measure  of  time. 


504 


CONGL  US  ION. 


In  the  future  I  see  open  fields  for  far  more  important 
researches.  Phychology  will  be  securely  based  on  the 
foundation  already  well  laid  by  Mr.  Herbert  Spencer,  that 
of  the  necessary  acquirement  of  each  mental  power  and 
capacity  by  gradation.  Much  light  will  be  thrown  on  the 
origin  of  man  and  his  history. 

Authors  of  the  highest  eminence  seem  to  be  fully  satisfied 
with  the  view  that  each  species  has  been  independently 
created.  To  my  mind  it  accords  better  with  what  we 
know  of  the  laws  impressed  on  matter  by  the  Creator,  that 
the  production  and  extinction  of  the  past  and  present  in¬ 
habitants  of  the  world  should  have  been  due  to  secondary 
causes,  like  those  determining  the  birth  and  death  of  the 
individual.  When  I  view  all  beings  not  as  special  creations, 
but  as  the  lineal  descendants  of  some  few  beings  which  lived 
long  before  the  first  bed  of  the  Cambrian  system  was  de¬ 
posited,  they  seem  to  me  to  become  ennobled.  Judging  from 
the  past,  we  may  safely  infer  that  not  one  living  species  will 
transmit  its  unaltered  likeness  "to  a  distinct  futurity. 
And  of  the  species  now  living  very  few  will  transmit 
progeny  of  any  kind  to  a  far  distant  futurity;  for  the 
manner  in  which  all  organic  beings  are  grouped,  shows 
that  the  greater  number  of  species  in  each  genus,  and  all 
the  species  in  many  genera,  have  left  no  descendants, 
but  have  become  utterly  extinct.  We  can  so  far  take  a 
prophetic  glance  into  futurity  as  to  foretell  that  it  will  be 
the  common  and  widely  spread  species,  belonging  to  the 
larger  and  dominant  groups  within  each  class,  which  will 
ultimately  prevail  and  procreate  new  and  dominant  species. 
As  all  the  living  forms  of  life  are  the  lineal  descendants  of 
those  which  lived  long  before  the  Cambrian  epoch,  we  may 
feel  certain  that  the  ordinary  succession  by  generation  has 
never  once  been  broken,  and  that  no  cataclysm  has  deso¬ 
lated  the  whole  world.  Hence,  we  may  look  with  some 
confidence  to  a  secure  future  of  great  length.  And  as 
natural  selection  works  solely  by  and  for  the  good  of  each 
being,  all  corporeal  and  mental  endowments  will  tend  to 
progress  toward  perfection. 

It  is  interesting  to  contemplate  a  tangled  bank,  clothed 
with  many  plants  of  many  kinds,  with  birds  singing  on  the 
bushes,  with  various  insects  flitting  about,  and  with  worms 
crawling  through  the  damp  earth,  and  to  reflect  that  these 


CONCLUSION ; 


505 


elaborately  constructed  forms,  so  different  from  each  other, 
and  dependent  upon  each  other  in  so  complex  a  manner, 
have  all  been  produced  by  laws  acting  around  us.  These 
laws,  taken  in  the  largest  sense,  being  Growth  with  repro¬ 
duction;  Inheritance  which  is  almost  implied  by  reproduc¬ 
tion;  Variability  from  the  indirect  and  direct  action  of  the 
conditions  of  life,  and  from  use  and  disuse:  a  Ratio  of  In¬ 
crease  so  high  as  to  lead  to  a  Struggle  for  Life,  and  as  a 
consequence  to  Natural  Selection,  entailing  Divergence  of 
Character  and  the  Extinction  of  less  improved  forms. 
Thus,  from  the  war  of  nature,  from  famine  and  death,  the 
most  exalted  object  which  we  are  capable  of  conceiving, 
namely,  the  production  of  the  higher  animals,  directly  fol¬ 
lows.  There  is  grandeur  in  this  view  of  life,  with  its  sev¬ 
eral  powers,  having  been  originally  breathed  by  the  Creator 
into  a  few  forms  or  into  one;  and  that,  while  this  planet 
has  gone  circling  on  according  to  the  fixed  law  of  gravity, 
from  so  simple  a  beginning  endless  forms  most  beautiful 
and  most  wonderful  have  been,  and  are  being  evolved. 


M)  /Y^CU^ 


GLOSSARY 

OF  THE 

PRINCIPAL  SCIENTIFIC  TERMS  USED  IN  THE 

PRESENT  VOLUME.* 


Aberrant. — Forms  or  groups  of  animals  or  plants  which,  deviate 
in  important  characters  from  their  nearest  allies,  so  as  not  to 
be  easily  included  in  the  same  group  with  them,  are  said  to 
be  aberrant. 

Aberration  (in  Optics). — In  the  refraction  of  light  by  a  convex  lens 
the  rays  passing  through  different  parts  of  the  lens  are  brought 
to  a  focus  at  slightly  different  distances — this  is  called  spherical 
aberration;  at  the  same  time  the  colored  rays  are  separated  by 
the  prismatic  action  of  the  lens  and  likewise  brought  to  a  focus 
at  different  distances — this  is  chromatic  aberration. 

Abnormal. — Contrary  to  the  general  rule. 

Aborted. — An  organ  is  said  to  be  aborted,  when  its  development 
has  been  arrested  at  a  very  early  stage. 

Albinism. — Albinos  are  animals  in  which  the  usual  coloring  matters 
characteristic  of  the  species  have  not  been  produced  in  the 
skin  and  its  appendages.  Albinism  is  the  state  of  being  an 
Albino. 

Alg^e. — A  class  of  plants  including  the  ordinary  sea- weeds  and  the 
filamentous  fresh-water  weeds. 

Alternation  of  Generations. — This  term  is  applied  to  a  peculiar 
mode  of  reproduction  which  prevails  among  many  of  the  lower 
animals,  in  which  the  egg  produces  a  living  form  quite  different 
from  its  parent,  but  from  which  the  parent-form  is  reproduced 
by  a  process  of  budding,  or  by  the  division  of  the  substance  of 
the  first  product  of  the  egg. 

Ammonites. — A  group  of  fossil,  spiral,  chambered  shells,  allied  to 
the  existing  pearly  Nautilus,  but  having  the  partitions  between 
the  chambers  waved  in  complicated  patterns  at  their  junction 
with  the  outer  wall  of  the  shell. 

*1  am  indebted  to  the  kindness  of  Mr.  W.  S.  Dallas  for  this  Glossary, 

whieh  has  been  given  because  several  readers  have  complained  to  me  that 

gome  of  the  terms  used  were  unintelligible  to  them.  Mr.  Dallas  has 

endeavored  to  give  the  explanations  of  the  terms  in  as  popular  a  form  as 

possible.  * 


508 


GLOSSARY. 


Analogy,— That  resemblance  of  structures  which  depends  upon 
eimibinty  of  function,  as  in  the  wings  of  insects  and  birds1 

of  eachother168  ***  Said  t0  b°  be  analo9OU8>  and  to  be  analogues 

ANmALeuLE  —  A  minute  animal:  generally  applied  to  those  visible 
only  by  the  microscope. 

Annelids  —A  class  of  worms  in  which  the  surface  of  the  body 
exhibits  a  more  or  less  distinct  division  into  rings  or  segments, 
generally  provided  with  appendages  for  locomotion  and  with 
gills.  It  includes  the  ordinary  marine  worms,  the  earth-worms 
and  the  leeches.  ’ 

ANTlIlN±,T^0i.nted)  orga“s  aPPended  to  the  head  in  Insects,  Crusta- 
cea  and  Centipedes,  and  not  belonging  to  the  mouth. 

jie  summits  of  the  stamens  of  flowers,  in  which  the 
pollen  or  fertilizing  dust  is  produced. 

maUa^'  Apla°entata  or  Aplacental  Mammals.  See  Mam- 

Archetypal.— Of  or  belonging  to  the  Archetype,  or  ideal  primitive 
izefl1  UP°U  Wblcb  a11  tbe  bein£s  of  a  group  seem  to  be  organ- 

AHT^LATA’~ngrrtndivision  of  tbe  Animal  Kingdom  character- 
tin^genDr^Uj  by  bavmg  the  surface  of  the  body  divided  into 
rings  called  segments,  a  greater  or  less  number  of  which  are 

Centipedes)Wlth  Jointed  leSs  (such  as  Insects,  Crustaceans  and 

Asymmetrical. — Having  the  two  sides  unlike. 

Atrophied.  Arrested  in  development  at  a  very  early  stage. 

B  alanus.  The  genus  including  the  common  Acorn-shells  which 
li\  e  in  abundance  on  the  rocks  of  the  sea-coast. 

B  atr  achians.  A  class  of  animals  allied  to  the  Reptiles,  but  under¬ 
going  a  peculiar  metamorphosis,  in  which  the  young  animal  is 

!“nyd  rwTs°)  “d  “es  by  «illS-  4*.“ 

B°'Tdays7rLg?ave‘rSPOrted  W°CkS  °f  6t0ne  generaUy  imbedded 

clas.s  °if  ma!'in1e  Mollusca>  or  soft-bodied  animals, 

a  stalWvl  Wnb  a  blVal+V;e  sbeb’  attached  to  submarine  objects  by 
a  stalk  which  passes  through  an  aperture  in  one  of  the  valves 

ZriedZte  Zuth  £ed  armS’  bj  ‘he  aCti0“  °f  Which  food  ia 

Branchial— Gills  or  organs  for  respiration  in  water 
Branchial.— Pertaining  to  gills  or  branchi®. 


CAMBmAN  System.-A  series  of  very  ancient  Paleozoic  rocks 
txjtween  the  Laurentian  and  the  Silurian.  Until  recently  thei 
were  regarded  as  the  oldest  fossiliferous  rocks 

CA™<f  he  Dog'fami1^  deluding  the  Dog,  Wolf,  Fox,  Jackal, 
Carapace.— The  shell  enveloping  the  anterior  part  of  the  body  in 


GLOSSARY :  509 

Crustaceans  generally;  applied  also  to  tlie  hard  shelly  pieces  of 
the  Cirripedes. 

Carboniferous. — This  term  is  applied  to  the  great  formation  which 
includes,  among  other  rocks,  the  coal-measures.  It  belongs  to 
the  oldest,  or  Palaeozoic,  system  of  formations. 

Caudal  — Of  or  belonging  to  the  tail. 

Cephalopods. — The  highest  class  of  the  Mollusca,  or  soft- bodied 
animals,  characterized  by  having  the  mouth  surrounded  by  a 
greater  or  less  number  of  fleshy  arms  or  tentacles,  which,  m 
most  living  species,  are  furnished  with  sucking-cups.  ( Exam¬ 
ples ,  Cuttle-fish,  Nautilus.) 

Cetacea. — An  order  of  Mammalia,  including  the  Whales,  Dolphins, 
etc.,  having  the  form  of  the  body  fish-like,  the  skin  naked,  and 
only  the  fore  limbs  developed. 

Chelonia. — An  order  of  Reptiles  including  the  Turtles,  Tortoises, 
etc. 

Cirripedes. — An  order  of  Crustaceans  including  the  Barnacles  and 
Acorn-shells.  Their  young  resemble  those  of  many  other  Crus¬ 
taceans  in  form;  but  when  mature  they  are  always  attached  to 
other  objects,  either  directly  or  by  means  of  a  stalk,  and  their 
bodies  are  enclosed  by  a  calcareous  shell  composed  of  several 
pieces,  two  of  which  can  open  to  give  issue  to  a  bunch  of  curled, 
jointed  tentacles,  which  represent  the  limbs. 

Coccus. — The  genus  of  Insects  including  the  Cochineal.  In  these 
the  male  is  a  minute,  winged  fly,  and  the  female  generally  a 
motionless,  berry-like  mass. 

COCOON. — A  case  usually  of  silky  material,  in  which  insects  are  fre¬ 
quently  enveloped  during  the  second  or  resting-stage  (pupa)  of 
their  existence.  The  term  “cocoon-stage”  is  here  used  as 
equivalent  to  “  pupa-stage.” 

Cgelospermous. — A  term  applied  to  those  fruits  of  the  Umbelliferae 
which  have  the  seed  hollowed  on  the  inner  face. 

Coleoptera. — Beetles,  an  order  of  Insects,  having  a  biting  mouth 
and  the  first  pair  of  wings  more  or  less  horny,  forming  sheaths 
for  the  second  pair,  and  usually  meeting  in  a  straight  line  down 
the  middle  of  the  back. 

Column. — A  peculiar  organ  in  the  flowers  of  Orchids,  in  winch 
the  stamens,  style  and  stigma  (or  the  reproductive  parts)  are 
united. 

Composite  or  Compositous  Plants. — Plants  in  which  the  inflores¬ 
cence  consists  of  numerous  small  flowers  (florets)  brought 
together  into  a  dense  head,  the  base  of  which  is  inclosed  by  a 
common  envelope.  {Examples,  the  Daisy,  Dandelions,  etc.) 

Conferva. — The  filamentous  weeds  of  fresh  water. 

Conglomerate. — A  rock  made  up  of  fragments  of  rock  or  pebbles, 
cemented  together  by  some  other  material. 

Corolla. — The  second  envelope  of  a  flower  usually  composed  of 
colored,  leaf-like  organs  (petals),  which  may  be  united  by  their  ' 
edges  either  in  the  basal  part  or  throughout. 

Correlation. — The  normal  coincidence  of  one  phenomenon,  charac¬ 
ter,  etc.,  with  another. 


510 


GLOSSARY. 


Corymb.— A  bunch  of  flowers  in  which  those  springing  from  the 
lower  part  of  the  flower-stalks  are  supported  on  long  stalks  so  as 
to  be  nearly  on  a  level  with  the  upper  ones. 

Cotyledons. — The  first  or  seed-leaves  of  plants. 

Crustaceans. — A  class  of  articulated  animals,  having  the  skin  of 
the  body  generally  more  or  less  hardened  by  the  deposition  of 
calcareous  matter,  breathing  by  means  of  gills.  (Examples, 
Crab,  Lobster,  Shrimp,  etc.) 

Curculio.  The  old  generic  term  for  the  Beetles  known  as  Weevils, 
characterized  by  their  four  jointed  feet,  and  by  the  head  being 
produced  into  a  sort  of  beak,  upon  the  sides  of  which  the 
antennae  are  inserted. 

Cutaneous. — Of  or  belonging  to  the  skin. 

Degradation.— The  wearing  down  of  land  by  the  action  of  the  sea 
or  of  meteoric  agencies. 

Denudation.— The  wearing  away  of  the  surface  of  the  land  by 
water. 

Devonian  System  or  Formation.— A  series  of  Palaeozoic  rocks, 
including  the  Old  Red  Sandstone. 

Dicotyledons  or  Dicotyledonous  Plants.— A  class  of  plants 
characterized  by  having  two  seed-leaves,  by  the  formation  of  new 
wood  between  the  bark  and  the  old  wood  (exogenous  growth) 
and  by  the  reticulation  of  the  veins  of  the  leaves.  The  parts  of 
the  flowers  are  generally  in  multiples  of  five. 

Differentiation. — The  separation  or  discrimination  of  parts  or 
organs  which  in  simpler  forms  of  life  are  more  or  less  united. 

Dimorphic.— Having  two  distinct  forms.— Dimorphism  is  the  condi  - 
dition  of  the  appearance  of  the  same  species  under  two  dissimilar 
forms. 

Dioecious.—  Having  the  organs  of  the  sexes  upon  distinct  indi¬ 
viduals. 

Diorite.  —A  peculiar  form  of  Greenstone. 

Dorsal. — Of  or  belonging  to  the  back. 

Edentata.— A  peculiar  order  of  Quadrupeds,  characterized  by  the 
absence  of  at  least  the  middle  incisor  (front)  teeth  in  both  jaws. 
{Examples,  the  Sloths  and  Armadillos.) 

Elytra. — The  hardened  fore- wings  of  Beetles,  serving  as  sheaths 
for  the  membranous  hind-wings,  which  constitute  the  true 
organs  of  flight. 

Embryo.— The  young  animal  undergoing  development  within  the 
egg  or  womb. 

Embryology. — The  study  of  the  development  of  the  embryo. 

Endemic. — Peculiar  to  a  given  locality. 

Entomostraca.  A  division  of  the  class  Crustacea,  having  all  the 
segments  of  the  body  usually  distinct,  gills  attached  to  the  feet 
or  organs  of  the  mouth,  and  the  feet  fringed  with  fine  hairs. 
They  are  generally  of  small  size. 

Eocene.  The  earliest  of  the  three  divisions  of  the  Tertiarv  epoch 
of  geologists.  Rocks  of  this  age  contain  a  small  proportion  of 
shells  identical  with  species  now  living. 


GLOSSARY. 


511 


Ephemerous  Insects. — Insects  allied  to  the  May-fly. 

Fauna. — The  totality  of  the  animals  naturally  inhabiting  a  certain 
country  or  region,  or  which  have  lived  during  a  given  geological 
period. 

Felidae. — The  Cat-family. 

Feral. — Having  become  wild  from  a  state  of  cultivation  or  domesti¬ 
cation. 

Flora.— The  totality  of  the  plants  growing  naturally  in  a  country, 
or  during  a  given  geological  period. 

Florets. — Flowers  imperfectly  developed  in  some  respects,  and  col¬ 
lected  into  a  dense  spike  or  head,  as  in  the  Grasses,  the  Dande¬ 
lion,  etc. 

Fcetal. — Of  or  belonging  to  the  foetus,  or  embryo  in  course  of 
development. 

Foraminifera. — A  class  of  animals  of  very  low  organization  and 
generally  of  small  size,  having  a  jelly-like  body,  from  the  sur¬ 
face  of  which  delicate  filaments  can  be  given  off  and  retracted  for 
the  prehension  of  external  objects,  and  having  a  calcareous  or 
sandy  shell,  usually  divided  into  chambers  and  perforated  with 
small  apertures. 

Fossiliferous. — Containing  fossils. 

Fossorial. — Having  a  faculty  of  digging.  The  Fossorial  Hymen- 
optera  are  a  group  of  Wasp-like  Insects,  wrliich  burrow  in  sandy 
soil  to  make  nests  for  their  young. 

Frenum  (pi.  Frena). — A  small  band  or  fold  of  skin. 

Fungi  (sing.  Fungus). — A  class  of  cellular  plants,  of  which  Mush¬ 
rooms,  Toadstools  and  Moulds,  are  familiar  examples. 

Furcula. — The  forked  bone  formed  by  the  union  of  the  collar-bones 
in  many  birds,  such  as  the  common  Fowl. 

Gallinaceous  Birds. — An  order  of  Birds  of  which  the  common 
Fowl,  Turkey  and  Pheasant,  are  well-known  examples. 

Gallus. — The  genus  of  birds  which  includes  the  common  Fowl. 

Ganglion. — A  swelling  or  knot  from  which  nerves  are  given  off  as 
from  a  center. 

Ganoid  Fishes. — Fishes  covered  with  peculiar  enameled  bony 
scales.  Most  of  them  are  extinct. 

Germinal  Vesicle. — A  minute  vesicle  in  the  eggs  of  animals,  from 
which  the  development  of  the  embryo  proceeds. 

Glacial  Period. — A  period  of  great  cold  and  of  enormous  extension 
of  ice  upon  the  surface  of  the  earth.  It  is  believed  that  glacial 
periods  have  occurred  repeatedly  during  the  geological  history  of 
the  earth,  but  the  term  is  generally  applied  to  the  close  of  the 
Tertiary  epoch,  when  nearly  the  whole  of  Europe  was  subjected 
to  an  arctic  climate. 

Gland. — An  organ  which  secretes  or  separates  some  peculiar  product 
from  the  blood  or  sap  of  animals  or  plants. 

Glottis. — The  opening  of  the  windpipe  into  the  oesophagus  or 
gullet. 

Gneiss. — A  rock  approaching  granite  in  composition,  but  more  or  less 


512 


GLOSSARY. 


laminated,  and  really  produced  by  the  alteration  of  a  sedimentary 
deposit  after  its  consolidation. 

Grallatores. — The  so-called  Wading-birds  (Storks,  Cranes,  Snipes, 
etc.),  which  are  generally  furnished  with  long  legs,  bare  of 
feathers  above  the  heel,  and  have  no  membranes  between  the 
toes. 

Granite.— A  rock  consisting  essentially  of  crystals  of  felspar  and 
mica  in  a  mass  of  quartz. 

Habitat.— The  locality  in  which  a  plant  or  animal  naturally  lives. 

Hemiptera. — An  order  or  sub-order  of  Insects,  characterized  by  the 
possession  of  a  jointed  beak  or  rostrum,  and  by  having  the  fore¬ 
wings  horny  in  the  basal  portion  and  membranous  at  the 
extremity,  where  they  cross  each  other.  This  group  includes 
the  various  species  of  Bugs. 

Hermaphrodite. — Possessing  the  organs  of  both  sexes. 

Homology. — That  relation  between  parts  which  results  from  their 
development  from  corresponding  embryonic  parts,  either  in 
different  animals,  as  in  the  case  of  the  arm  of  man.  the  fore  leg 
of  a  quadruped,  and  the  wing  of  a  bird;  or  in  the  same  indi¬ 
vidual,  as  in  the  case  of  the  fore  and  hind  legs  in  quadrupeds, 
and  the  segments  or  rings  and  their  appendages  of  which  the 
body  of  a  worm,  a  centipede,  etc.,  is  composed.  The  latter  is 
called  serial  homology.  The  parts  which  stand  in  such  a  relation 
to  each  other  are  said  to  be  homologous,  and  one  such  part  or  organ 
is  called  the  homologue  of  the  other.  In  different  plants  the 
parts  of  the  flower  are  homologous,  and  in  general  these  parts 
are  regarded  as  homologous  with  leaves. 

Homoptera.— An  order  or  sub -order  of  Insects  having  (like  the 
Hemiptera)  a  jointed  beak,  but  in  which  the  fore- wings  are 
either  wholly  membranous  or  wholly  leathery.  The  Cicada ?, 
Frog-hoppers,  and  Aphides,  are  well-known  examples. 

Hybrid.— The  offspring  of  the  union  of  two  distinct  species. 

Hymenoptera.— An  order  of  Insects  possessing  biting  jaws  and 
usually  four  membranous  wings  in  which  there  are  a  few  veins. 
Bees  and  Wasps  are  familiar  examples  of  this  group. 
Hypertrophied.— Excessively  developed. 

Ichneumonid^e. — A  family  of  Hymenopterous  insects,  the  members 
of  which  lay  their  eggs  in  the  bodies  or  eggs  of  other  insects. 

Imago.— The  perfect  (generally  winged)  reproductive  state  of  an 
insect. 

Indigens.— The  aboriginal  animal  or  vegetable  inhabitants  of  a 
country  or  region. 

Inflorescence. — The  mode  of  arrangement  of  the  flowers  of  plants. 

Infusoria.  A  class  of  microscopic  Animalcules,  so  called  from  their 
having  originally  been  observed  in  infusions  of  vegetable 
matters.  1  hey  consist  of  a  gelatinous  material  inclosed  in  & 
delicate  membrane,  the  whole  or  part  of  which  is  furnished  with 
short  vibrating  hairs  (called  cilia),  by  means  of  which  the 
animalcules  swim  through  the  water  or  convey  the  minute  parti¬ 
cles  of  their  food  to  the  orifice  of  the  mouth. 


GLOSSARY. 


513 


Insectivorous. — Feeding  on  Insects. 

Invertebrata,  or  Invertebrate  Animals. — Those  animals  which 
do  not  possess  a  backbone  or  spinal  column. 

Lacunae. — Spaces  left  among  the  tissues  in  some  of  the  lower 
animals,  and  serving  in  place  of  vessels  for  the  circulation  of  the 
fluids  of  the  body. 

Lamellated. — Furnished  with  lamellae  or  little  plates. 

Larva  (pi.  Larvae). — The  first  condition  of  an  insect  at  its  issuing 
from  the  egg,  when  it  is  usually  in  the  form  of  a  grub,  cater¬ 
pillar  or  maggot. 

Larynx. — The  upper  part  of  the  windpipe  opening  into  the  gullet 

Laurentian. — A  group  of  greatly  altered  and  very  ancient  rocks! 
which  is  greatly  developed  along  the  course  of  the  St.  Lawrence, 
whence  the  name.  It  is  in  these  that  the  earliest  known  traces 
of  organic  bodies  have  been  found. 

Leguminos^e. — An  order  of  plants  represented  by  the  common  Peas 
and  Beans,  having  an  irregular  flower  in  which  one  petal  stands 
up  like  a  wing,  and  the  stamens  and  pistil  are  inclosed  in  a 
sheath  formed  by  two  other  petals.  The  fruit  is  a  pod  (or 
legume). 

Lemurid^e. — A  group  of  four-handed  animals,  distinct  from  the 
Monkeys,  and  approaching  the  Insectivorous  Quadrupeds  in  some 
of  their  characters  and  habits.  Its  members  have  the  nostrils 
curved  or  twisted,  and  a  claw  instead  of  a  nail  upon  the  first 
finger  of  the  hind  hands. 

Lepidoptera. — An  order  of  Insects,  characterized  by  the  possession 
of  a  spiral  proboscis,  and  of  four  large  more  or  less  scaly  wings. 
It  includes  the  well-known  Butterflies  and  Moths. 

Littoral. — Inhabiting  the  sea-shore. 

Loess. — A  marly  deposit  of  recent  (Post- Tertiary)  date,  which  occu¬ 
pies  a  great  part  of  the  valley  of  the  Rhine. 

Malacostraca. — The  higher  division  of  the  Crustacea,  including 
the  ordinary  Crabs,  Lobsters,  Shrimps,  etc.,  together  with  the 
Wood-lice  and  Sand-hoppers. 

Mammalia. — The  highest  class  of  animals,  including  the  ordinary 
hairy  quadrupeds,  the  Whales  and  Man,  and  characterized  by 
the  production  of  living  young  which  are  nourished  after  birth 
by  milk  from  the  teats  (Mamma,  Mammary  glands)  of  the 
mother.  A  striking  difference  in  embryonic  development  has 
led  to  the  division  of  this  class  into  two  great  groups;  in  one  of 
these,  when  the  embryo  has  attained  a  certain  stage,  a  vascular 
connection,  called  the  placenta,  is  formed  between  the  embryo 
and  the  mother;  in  the  other  this  is  wanting,  and  the  young  are 
produced  in  a  very  incomplete  state.  The  former,  including  the 
greater  part  of  the  class,  are  called  Placental  mammals;  the 
latter,  or  Aplacental  mammals,  include  the  Marsupials  and  M0110- 
tremes  ( Ornithorhynchus ). 

Mammiferous. — Having  mammae  or  teats  (see  Mammalia). 
Mandibles  ia  Insects. — The  first  or  uppermost  pair  of  jaws,  which 


514 


GLOSSARY, 


are  generally  solid,  liorny,  biting  organs.  In  Birds  the  term  is 
applied  to  both  jaws  witb  their  horny  coverings.  In  Quadrupeds 
the  mandible  is  properly  the  lower  jaw. 

Marsupials. — An  order  of  Mammalia  in  which  the  young  are  born 
in  a  very  incomplete  state  of  development  and  carried  by  the 
mother,  while  sucking,  in  a  ventral  pouch  (marsupium),  such  as 
the  Kangaroos,  Opossums,  etc.  (see  Mammalia). 

MaxillvE  in  Insects. — The  second  or  lower  pair  of  jaws,  which  are 
composed  of  several  joints  and  furnished  with  peculiar  jointed 
appendages  called  palpi  or  feelers. 

Melanism. — The  opposite  of  albinism;  an  undue  development  of 
coloring  material  in  the  skin  and  its  appendages. 

Metamorphic  Rocks. — Sedimentary  rocks  which  have  undergone 
alteration,  generally  by  the  action  of  heat,  subsequently  to  their 
deposition  and  consolidation. 

Mollusca. — One  of  the  great  divisions  of  the  Animal  Kingdom, 
including  those  animals  which  have  a  soft  body,  usually  furnished 
with  a  shell,  and  in  which  the  nervous  ganglia,  or  centers,  pre¬ 
sent  no  definite  general  arrangement.  They  are  generally 
known  under  the  denomination  of  “shell-fish;”  the  cuttle-fish, 
and  the  common  snails,  whelks,  oysters,  mussels  and  cockles, 
may  serve  as  examples  of  them. 

Monocotyledons,  or  Monocotyledonous  Plants. — Plants  in 
which  the  seed  sends  up  only  a  single  seed-leaf  (or  cotyledon); 
characterized  by  the  absence  of  consecutive  layers  of  wood  in  the 
stem  (endogenous  growth),  by  the  veins  of  the  leaves  being 
generally  straight,  and  by  the  parts  of  the  flowers  being  gener¬ 
ally  in  multiples  of  three.  {Examples,  Grasses,  Lilies,  Orchids, 
Palms,  etc.) 

Moraines. — The  accumulations  of  fragments  of  rock  brought  down 
by  glaciers. 

Morphology. — The  law  of  form  or  structure  independent  of  func¬ 
tion. 

Mysis-stage. — A  stage  in  the  development  of  certain  Crustaceans 
(Prawns),  in  which  they  closely  resemble  the  adults  of  a  genus 
{My sis)  belonging  to  a  slightly  lower  group. 

Nascent. — Commencing  development. 

Natatory. — Adapted  for  the  purpose  of  swimming. 

Nauplius-form. — The  earliest  stage  in  the  development  of  many 
Crustacea,  especially  belonging  to  the  lower  groups.  In  this 
stage  the  animal  has  a  short  body,  with  indistinct  indications  ol 
a  division  into  segments,  and  three  pairs  of  fringed  limbs.  This 
form  of  the  common  fresh- water  Cyclops  was  described  as  a  dis¬ 
tinct  genus  under  the  name  of  Nauplius. 

Neuration.— The  arrangement  of  the  veins  or  nervures  in  the 
wings  of  Insects. 

Nictitating  Membrane. — A  semi-transparent  membrane,  which 
can  be  drawn  across  the  eye  in  Birds  and  Reptiles,  either  to 
moderate  the  effects  of  a  strong  light  or  to  sweep  particles  of 
dust,  etc.,  from  the  surface  of  the  eye. 


GLOSSARY. 


515 


Neuters.—  Imperfectly  developed  females  of  certain  social  insects 
(such  as  Ants  and  Bees),  which  perform  all  the  labors  of  the 
community.  Hence  they  are  also  called  workers. 

Ocelli. — The  simple  eyes  or  stemmata  of  Insects,  usually  situated 
on  the  crown  of  the  head  between  the  great  compound  eyes. 

(Esophagus.— The  gullet. 

Oolitic. — A  great  series  of  secondary  rocks,  so  called  from  the 
texture  of  some  of  its  members,  which  appear  to  be  made  up  of 
a  mass  of  small  egg-like  calcareous  bodies. 

Operculum. — A  calcareous  plate  employed  by  many  Mollusca  to 
close  the  aperture  of  their  shell.  The  opercular  valves  of  Cirri- 
pedes  are  those  which  close  the  aperture  of  the  shell. 

Orbit. — The  bony  cavity  for  the  reception  of  the  eye. 

Organism. — An  organized  being,  whether  plant  or  animal. 

Orthospermous. — A  term  applied  to  those  fruits  of  the  Umbelliferse 
which  have  the  seed  straight. 

Osculant. — Forms  or  groups  apparently  intermediate  between  and 
connecting  other  groups  are  said  to  be  osculant. 

Ova. — Eggs. 

Ovarium  or  Ovary  (in  plants). — The  lower  part  of  the  pistil  or 
female  organ  of  the  flower,  containing  the  ovules  or  incipient 
seeds;  by  growth  after  the  other  organs  of  the  flower  have 
fallen,  it  usually  becomes  converted  into  the  fruit. 

Ovigerous. — Egg-bearing. 

Ovules  (of  plants). — The  seeds  in  the  earliest  condition. 

Pachyderms. — A  group  of  Mammalia,  so  called  from  their  thick 
skins,  and  including  the  Elephant,  Rhinocerous,  Hippopotamus, 
etc. 

Palaeozoic. — The  oldest  system  of  fossiliferous  rocks. 

Palpi. — Jointed  appendages  to  some  of  the  organs  of  the  mouth  in 
Insects  and  Crustacea. 

Papilionace^e. — Anorder  of  Plants  (see  Leguminos^e). — The  flowers 
of  these  plants  are  called  papilionaceous,  or  butterfly-like,  from 
the  fancied  resemblance  of  the  expanded  superior  petals  to  the 
wings  of  a  butterfly. 

Parasite. — An  animal  or  plant  living  upon  or  in,  and  at  the 
expense  of,  another  organism. 

Parthenogenesis. — The  production  of  living  organisms  from  unim¬ 
pregnated  eggs  or  seeds. 

Pedunculated. — Supported  upon  a  stem  or  stalk.  The  peduncu¬ 
lated  oak  has  its  acorns  borne  upon  a  footstool. 

Peloria  or  Pelorism. — The  appearance  of  regularity  of  structure 
in  the  flowers  of  plants  which  normally  bear  irregular  flowers. 

Pelvis. — The  bony  arch  to  which  the  hind  limbs  of  vertebrate 
animals  are  articulated. 

Petals. — The  leaves  of  the  corolla,  or  second  circle  of  organs  in  a 
flower.  They  are  usually  of  delicate  texture  and  brightly  colored. 

Phyllodineous. — Having  flattened,  leaf-like  twigs  or  leaf-stalks 
instead  of  true  leaves. 


516 


GLOSSARY. 


1  tgment.  I  he  coloring  material  produced  generally  in  the  super¬ 
ficial  parts  of  animals.  The  cells  secreting  it  are  called  pigment - 

C6LC8 • 

Pinnate.— Bearing  leaflets  on  each  side  of  a  central  stalk. 

Pistils.— The  female  organs  of  a  flower,  which  occupy  a  position  in 
the  center  of  the  other  floral  organs.  The  pistil  is  generally 
divisible  into  the  ovary  or  germen,  the  style  and  the  stigma. 
Placentalia,  Placentata,  or  Placental ‘Mammals.— See  Mam 
malia. 

Plantigrades.— Quadrupeds  which  walk  upon  the  whole  sole  c< 
the  foot,  like  the  Bears. 

Plastic. — Readily  capable  of  change. 

Pleistocene  Period.— Ths  latest  portion  of  the  Tertiary  epoch. 

1  lumule  (in  plants). — The  minute  bud  between  the  seed-leaves  of 
newly-germinated  plants. 

Plutonic  Rocks.— Rocks  supposed  to  have  been  produced  by 

^  igneous  action  in  the  depths  of  the  earth. 

Pollen.— The  male  element  in  flowering  plants;  usually  a  fine  dust 
produced  by  the  anthers,  which,  by  contact  with  the  stigma 
effects  the  fecundation  of  the  seeds.  This  impregnation  is 
brought  about  by  means  of  tubes  ( pollen-tubes )  which  issue  from 
the  pollen-grains  adhering  to  the  stigma,  and  penetrate  through 
the  tissues  until  they  reach  the  ovary. 

Polyandrous  (flowers). — Flowers  having  many  stamens. 

Polygamous  Plants. — Plants  in  which  some  flowers  are  unisexual 
and  others  hermaphrodite.  The  unisexual  (male  and  female) 
flowers,  may  be  on  the  same  or  on  different  plants. 

Polymorphic. — Presenting  many  forms. 

Polyzoary.— The  common  structure  formed  by  the  cells  of  the 
Polyzoa,  such  as  the  well-known  Sea-mats. 

Prehensile. — Capable  of  grasping. 

Prepotent. — Having  a  superiority  of  power. 

Primaries.— The  feathers  forming  the  tip  of  the  wing  of  a  bird,  and 
inserted  upon  that  part  which  represents  the  hand  of  man 

Processes.— Projecting  portions  of  bones,  usually  for  the  attach¬ 
ment  of  muscles,  ligaments,  etc. 

Propolis.— A  resinous  material  collected  by  the  Hive-Bees  from  the 
opening  buds  of  various  trees. 

Protean. — Exceedingly  variable. 

Protozoa.— The  lowest  great  division  of  the  Animal  Kingdom, 
lhese  animals  are  composed  of  a  gelatinous  material  and  show 
scarcely  any  trace  of  distinct  organs.  The  Infusoria,  Foramini- 
fera  and  Sponges,  with  some  other  forms,  belong  to  this  division. 

Pupa  (pi.  Pup^e)  — The  second  stage  in  the  development  of  an 
Insect,  from  which  it  emerges  in  the  perfect  (winged)  reproduc¬ 
tive  form.  In  most  insects  the  pupal  stage  is  passed  in  perfect 
repose.  The  chrysalis  is  the  pupal  state  of  Butterflies. 

Ramus.— One  half  of  the  lower  iaw  in  the  Mammalia.  The  portion 
which  rises  to  articulate  with  the  skull  is  called  the  ascendina 
ramus.  * 


GLOSSARY. 


517 


Radicle. — The  minute  root  of  an  embryo  plant. 

Range. — The  extent  of  country  over  which  a  plant  or  animal  is 
naturally  spread.  Range  in  time  expresses  the  distribution  of  a 
species  or  group  through  the  fossiliferous  beds  of  the  earth’s 
crust. 

Retina. — The  delicate  inner  coat  of  the  eye,  formed  by  nervous 
filaments  spreading  from  the  optic  nerve  and  serving  for  the 
perception  of  the  impressions  produced  by  light. 

Retrogression. — Backward  development.  When  an  animal,  as  it 
approaches  maturity,  becomes  less  perfectly  organized  than 
might  be  expected  from  its  early  stages  and  known  relationships, 
it  is  said  to  undergo  a  retrograde  development  or  metamorphosis. 

Rhizopods. — A  class  of  lowly  organized  animals  (Protozoa),  having  a 
gelatinous  body,  the  surface  of  which  can  be  protruded  in  the 
form  of  root-like  processes  or  filaments,  which  serve  for  locomo¬ 
tion  and  the  prehension  of  food.  The  most  important  order  is 
that  of  the  Foraminifera. 

Rodents. — The  gnawing  Mammalia,  such  as  the  Rats,  Rabbits  and 
Squirrels.  They  are  especially  characterized  by  the  possession 
of  a  single  pair  of  chisel-like  cutting  teeth  in  each  jaw,  between 
which  and  the  grinding  teeth  there  is  a  great  gap. 

Rubus. — The  Bramble  Genus. 

Rudimentary. — Very  imperfectly  developed. 

Ruminants. — The  group  of  Quadrupeds  which  ruminate  or  chew  the 
cud,  such  as  oxen,  sheep  and  deer.  They  have  divided  hoofs, 
and  are  destitute  of  front  teeth  in  the  upper  jaw. 

Sacral. — Belonging  to  the  sacrum,  or  the  bone  composed  usually  of 
two  or  more  united  vertebrae  to  which  the  sides  of  the  pelvis  in 
vertebrate  animals  are  attached. 

Sarcode. — The  gelatinous  material  of  which  the  bodies  of  the  lowest 
animals  (Protozoa)  are  composed. 

Scutell^e. — The  horny  plates  with  which  the  feet  of  birds  are 
generally  more  or  less  covered,  especially  in  front. 

Sedimentary  Formations. — Rocks  deposited  as  sediments  from 
water. 

Segments. — The  tranverse  rings  of  which  the  body  of  an  articulate 
animal  or  Annelid  is  composed. 

Sepals. — The  leaves  or  segments  of  the  calyx,  or  outermost  envelope 
of  an  ordinary  flower.  They  are  usually  green,  but  sometimes 
brightly  colored. 

Serratures. — Teeth  like  those  of  a  saw. 

Sessile. — Not  supported  on  a  stem  or  footstalk. 

Silurian  System. — A  very  ancient  system  of  fossiliferous  rocks 
belonging  to  the  earlier  part  of  the  Palaeozoic  series. 

Specialization. — The  setting  apart  of  a  particular  organ  for  the 
performance  of  a  particular  function. 

Spinal  Chord. — The  central  portion  of  the  nervous  system  in  the 
Vertebrata.  which  descends  from  the  brain  through  the  arches 
of  the  vertebrae,  and  gives  off  nearly  all  the  nerves  to  the  various 
organs  of  the  body. 


( 


518 


GLOSSARY. 


Stamens. — The  male  organs  of  flowering  plants,  standing  in  a  circle 
within  the  petals.  They  usually  consist  of  a  filament  and  an 
anther,  the  anther  being  the  essential  part  in  which  the  pollen, 
or  fecundating  dust,  is  formed. 

Sternum.— The  breast-bone. 

Stigma. — The  apical  portion  of  the  pistil  in  flowering  plants. 

Stipules. — Small  leafy  organs  placed  at  the  base  of  the  footstalks  of 
the  leaves  in  many  plants. 

Style. — The  middle  portion  of  the  perfect  pistil,  which  rises  like  a 
column  from  the  ovary  and  supports  the  stigma  at  its  summit. 

Subcutaneous.— Situated  beneath  the  skin. 

Suctorial. — Adapted  for  sucking. 

Sutures  (in  the  skull). — The  lines  of  junction  of  the  bones  of  which 
the  skull  is  composed. 

Tarsus  (pi.  Tarsi). — The  jointed  feet  of  articulate  animals,  such  as 
Insects. 

Teleostean  Fishes. — Fishes  of  the  kind  familiar  to  us  in  the 
present  day,  having  the  skeleton  usually  completely  ossified  and 
the  scales  horny. 

Tentacula  or  Tentacles. — Delicate  fleshy  organs  of  prehension 
or  touch  possessed  by  many  of  the  lower  animals. 

Tertiary. — The  latest  geological  epoch,  immediately  preceeding  the 
establishment  of  the  present  order  of  things. 

Trachea. — The  windpipe  or  passage  for  the  admission  of  air  to  the 
lungs. 

Tridactyle. — Three-fingered,  or  composed  of  three  movable  parts 
attached  to  a  common  base. 

Trilobites. — A  peculiar  group  of  extinct  Crustaceans,  somewhat 
resembling  the  Wood-lice  in  external  form,  and,  like  some  of 
them,  capable  of  rolling  themselves  up  into  a  ball.  Their 
remains  are  found  only  in  the  Palseozoic  rocks,  and  most  abund¬ 
antly  in  those  of  Silurian  age. 

Trimorphic. — Presenting  three  distinct  forms. 


Umbelliferae. — An  order  of  plants  in  which  the  flowers,  which 
contain  five  stamens  and  a  pistil  with  two  styles,  are  supported 
upon  footstalks  which  spring  from  the  top  of  the  flower  stem 
and  spread  out  like  the  wires  of  an  umbrella,  so  as  to  bring  all 
the  flowers  in  the  same  head  (umbel)  nearly  to  the  same  level. 
( Examples ,  Parsley  and  Carrot.) 

Ungulata. — Hoofed  quadrupeds. 

Unicellular. — Consisting  of  a  single  cell. 

Vascular. — Containing  blood-vessels. 

Vermiform. — Like  a  worm. 

Vertebrata;  or  Vertebrate  Animals, — The  highest  division  of 
the  animal  kingdom,  so  called  from  the  presence  in  most  cases  of 
a  backbone  composed  of  numerous  joints  or  vertebrce,  which  con¬ 
stitutes  the  center  of  the  skeleton  and  at  the  same  time  supports 
and  protects  the  central  parts  of  the  nervous  system. 


GLOJSSAHY. 


519 


Whorls.— The  circles  or  spiral  lines  in  which  the  parts  of  plants  are 
arranged  upon  the  axis  of  growth. 

Workers. — See  Neuters. 

Zoea-stage. — The  earliest  stage  in  the  development  of  many  of  the 
higher  Crustacea,  so  called  from  the  name  of  Zoea  applied  to 
these  young  animals  when  they  were  supposed  to  constitute  a 
peculiar  genus. 

Zooids. — In  many  of  the  lower  animals  (such  as  the  Corals,  Medusae, 
etc.)  reproduction  takes  place  in  two  ways,  namely,  by  means  of 
eggs  and  by  a  process  of  budding  with  or  without  separation 
from  the  parent  of  the  product  of  the  latter,  which  is  often  very 
di  fferent  from  that  of  the  egg.  The  individuality  of  the  species 
is  represented  by  the  whole  of  the  form  produced  between  two 
sexual  reproductions;  and  these  forms,  which  are  apparently 
individual  animals,  have  been  called  zooids. 


»  ,1 

i 

i 


INDEX 


Abberant  groups,  447. 

Abyssinia,  plants  of,  401. 

Acclimatization,  133. 

Adoxa,  205. 

Affinities  of  extinct  species,  356. 

- of  organic  beings,  445. 

Agassiz,  on  Amblyopsis,  133. 

- ,  on  groups  of  species  sud¬ 
denly  appearing,  342. 

- ,  on  prophetic  forms,  357. 

- ,  on  embryological  succession, 

366. 

- ,  on  the  Glacial  period,  389. 

- ,  on  embryological  charac¬ 
ters,  434. 

- ,  on  the  latest  tertiary  forms, 

329. 

• - ,  on  parallelism  of  embryo- 

logical  development  and  geo¬ 
logical  succession,  466. 

- ,  Alex.,  on  pedicellariae,  226. 

Algae  of  New  Zealand,  399. 

Alligators,  males,  fighting,  81. 

Alternate  generations,  456. 

Amblyopsis,  blind  fish,  133. 

America,  North,  productions  al¬ 
lied  to  those  of  Europe,  393. 

— = — , - ,  bowlders  and  glaciers 

of,  395. 

. - ,  South,  no  modern  forma¬ 

tions  on  west  coast,  322. 

Ammonites,  sudden  extinction  of, 
351. 

Anagallis,  sterility  of,  279. 

Analogy  of  variations,  150. 

Andaman  Islands  inhabited  by  a 
toad,  413. 

Ancylus,  407. 


Animals,  not  domesticated  from 
being  variable,  15. 

- ,  domestic,  descended  from 

several  stocks,  16. 

- , - ,  acclimatization  of,  134. 

Animals  of  Australia,  106. 

- with  thicker  fur  in  cold  cli¬ 
mates,  127.. 

- ,  blind,  in  caves,  131. 

- extinct,  of  Australia,  367. 

Anomma,  273. 

Antarctic  islands,  ancient  flora  of, 
419. 

Antechinus,  440. 

Ants  attending  aphides,  245. 

- ,  slave-making  instinct,  255. 

- ,  neuters,  structure  of,  272. 

Apes,  not  having  acquired  intel¬ 
lectual  powers,  214. 

Aphides,  attended  by  ants,  245. 
Aphis,  development  of,  460. 
Apteryx,  166. 

Arab  horses,  30. 

Aralo-Caspian  Sea,  367. 
Archeopteryx,  335. 

Archiac,  M.  de,  on  the  succession 
of  species,  353. 

Artichoke,  Jerusalem,  135, 
Ascension,  plants  of,  410. 
Asclepias,  pollen  of,  180. 
Asparagus,  383. 

Aspicarpa,  433. 

Asses,  striped,  152. 

- ,  improved  by  selection,  36. 

Ateuchus,  129. 

Aucapitaine,  on  land-shells,  417. 
Audubon,  on  habits  of  frigate- 
bird,  169. 


522 


INDEX. 


Audubon,  on  variation  in  birds' 
nests,  246. 

- ,  on  heron  eating  seeds,  409. 

Australia,  animals  of,  106. 

« - ,  dogs  of,  249. 

• - ,  extinct  animals  of,  367. 

- ,  European  plants  in,  398, 

- - ,  glaciers  of,  395. 

Azara,  on  hies  destroying  cattle, 
67. 

Azores,  flora  of,  388. 

Babington,  Mr. ,  on  British  plants, 
44 

Baer,  Von,  standard  of  Highness, 
116. 

- ,  comparison  of  bee  and  fish, 

364. 

- ,  embryonic  similarity  of  the 

Vertebrata,  458. 

Baker,  Sir  S.,  on  the  giraffe,  211. 
Balancement  of  growth,  139. 
Baleen,  216. 

Barberry,  flowers  of,  91. 

Barrande,  M.,  on  Silurian  colo 
nies,  344. 

- ,  on  the  succession  of  species, 

354. 

- ,  on  parallelism  of  palaeozoic 

formations,  356. 

- ,  on  affinities  of  ancient 

species,  357. 

Barriers,  importance  of,  373. 
Bates,  Mr. ,  on  mimetic  butterflies, 
443,  444. 

Batrachians  on  islands,  413. 

Bats,  how  structure  acquired,  166. 

- ,  distribution  of,  415. 

Bear,  catching  water-insects,  168. 
Beauty,  how  acquired,  189,  488. 
Bee,  sting  of,  194. 

- - ,  queen,  killing  rivals,  194. 

- ,  Australian,  extermination 

of,  70. 

Bees,  fertilizing  flowers,  68. 

- - ,  hive,  not  sucking  the  red 

clover,  88. 

- ,  hive,  cell  making  instinct, 

259. 

- ,  Ligurian,  88. 

- ,  variation  in  habits,  246. 


Bees,  parasitic,  255. 

- ,  humble,  cells  of,  260. 

Beetles,  wingless,  in  Madeira,  130. 

- with  deficient  tarsi,  129. 

Bentham,  Mr.,  on  British  plants, 
44. 

- ,  on  classification,  435. 

Berkeley,  Mr.,  on  seeds  in  salt 
water,  383. 

Bermuda,  birds  of,  412. 

Birds  acquiring  fear,  246. 

- ,  beauty  of,  191. 

- -  annually  cross  the  Atlantic, 

389. 

- ,  color  of,  on  continents,  127. 

- ,  footsteps,  and  remains  of, 

in  secondary  rocks,  335. 

- ,  fossil,  in  caves  of  Brazil, 

367. 

- ,  of  Madeira,  Burmuda  and 

Galapagos,  412,  413. 

- ,  song  of  males,  82. 

■ - ,  transporting  seeds,  387. 

- ,  waders,  408. 

- ,  wingless,  128,  166. 

Bizcacha,  376. 

- ,  affinities  of,  447. 

Bladder  for  swimming,  in  fish, 
175. 

Blindness  of  cave  animals,  130. 
Blyth,  Mr.,  on  distinctness  of 
Indian  cattle,  16. 

- ,  on  striped  hemionus,  138. 

- ,  on  crossed  geese,  284. 

Borrow,  Mr.,  on  the  Spanish 
pointer,  30. 

Borv  St.  Vincent,  on  Batrachians, 
413. 

Bosquet,  M.,  on  fossil  Chtha- 
malus,  336. 

Bowlders,  erratic,  on  the  Azores, 
388. 

Branchiae,  176,  177. 

- ,  of  crustaceans,  181. 

- ,  Braun,  Prof.,  on  the  seeds 

of  Fumariaceae,  206. 

Brent,  Mr.,  on  house-tumblers, 
248. 

Britain,  mammals  of,  415, 

Broca,  Prof.,  on  Natural  Selec- 
I  tion,  201. 


INDEX. 


Bronn,  Prof.,  on  duration  of 
specific  forms,  326. 

- ,  various  objections  by,  201. 

Brown,  Robert,  on  classification, 
432. 

- ,  Sequard,  on  inherited  muti¬ 
lations,  129. 

Busk,  Mr. ,  on  the  Polyzoa,  228. 

Butterflies,  mimetic,  443,  444, 
445. 

Buzareingues,  on  sterility  of  varie¬ 
ties,  304. 

Cabbage,  varieties  of,  crossed,  9. 

Calceolaria,  282. 

Canary-birds,  sterility  of  hybrids, 
282. 

Cape  de  Verde  Islands,  produc¬ 
tions  of,  418. 

- - ,  plants  of,  on  mountains, 

398. 

Cape  of  Good  Hope,  plants  of, 
121,  410. 

Carpenter,  Dr.,  on  foraminifera, 
364. 

Carthamus,  205. 

Catasetum,  184,  438. 

Cats,  with  blue  eyes,  deaf,  10. 

- ,  variation  in  habits  of,  247. 

-  curling  tail  when  going  to 

spring,  193. 

Cattle  destroying  fir-trees,  67. 

-  destroyed  by  flies  in  Para¬ 
guay,  67. 

- breeds  of,  locally  extinct, 

101. 

- ,  fertility  of  Indian  and  Euro¬ 
pean  breeds,  283. 

- ,  Indian,  16,  283. 

Cave,  inhabitants  of,  blind,  130. 

Cecidomyia,  456. 

Celts,  proving  antiquity  of  man, 
16. 

Centers  of  Creation,  378. 

Cephalopodae,  structures  of  eyes, 
180. 

- ,  development  of,  460. 

Cercopithecus,  tail  of,  223. 

Ceroxylus  laceratus,  216. 

Cervulus,  283. 

Cetacea,  teeth  and  hair,  137. 


523 

Cetacea,  development  of  the 
whalebone,  216. 

Cetaceans,  216. 

Ceylon,  plants  of,  399. 

Chalk  formation,  352. 

Characters,  divergence  of,  101. 

- ,  sexual,  variable,  141,  146. 

- ,  adaptive  or  analogical,  440. 

Charlock,  71. 

Checks  to  increase,  63. 

- ,  mutual,  65. 

Chelae  of  Crustaceans,  228. 
Chickens,  instinctive  tameness  of, 

,  249. 

Chironomus,  its  asexual  reproduc¬ 
tion,  456. 

Chthamalinae,  320. 

Chthamalus,  cretacean  species  of, 
336. 

Circumstances  favorable  to  selec¬ 
tion  of  domestic  products,  35, 

— - - to  natural  selection,  94. 

Cirripedes  capable  of  crossing,  93. 

- ,  carapace  aborted,  140. 

- ,  their  ovigerous  frena,  177. 

- ,  fossil,  336. 

- ,  larvae  of,  458. 

Claparede,  Prof.,  on  the  hair- 
claspers  of  the  Acaridae,  182. 
Clarke,  Rev.  W.  B.,  on  old 
glaciers  in  Australia,  396. 
Classification,  428. 

Clift,  Mr.,  on  the  succession  of 
types,  367. 

Climate,  effects  of,  in  checking 
increase  of  beings,  64. 

- ,  adaptation  of,  to  organisms* 

133. 

Climbing  plants,  175. 

- ,  development  of,  231. 

Clover  visited  by  bees,  88. 

Cobites,  intestine  of,  175, 
Cockroach,  71. 

Collections,  palaeontological,  poor, 
319. 

Color,  influenced  by  climate,  127. 

- ,  in  relation  to  attack  by  flies, 

,  189. 

Columba  livia,  parent  of  domes¬ 
tic  pigeons,  20. 

Colymbetes,  407. 


524 


INDEX. 


Compensation  of  growth,  139. 

Composite,  flowers  and  seeds  of, 
137. 

— — ,  outer  and  inner  florets  of, 
205. 

- - ,  male  flowers  of,  469. 

Conclusion,  general,  495. 

Conditions,  slight  changes  in, 
favorable  to  fertility,  296. 

Convergence  of  genera,  120. 

Coot,  169. 

Cope,  Prof.,  on  the  acceleration 
or  retardation  of  the  period  of 
reproduction,  177. 

Coral-islands,  seeds  drifted  to, 
385. 

- reefs,  indicating  movements 

of  earth,  385. 

Corn  crake,  170. 

Correlated  variation  in  domestic 
productions,  10. 

Coryanthes,  183. 

Creation,  single  centers  of,  378. 

Crinum,  281. 

Croll,  Mr.,  on  subaerial  denuda¬ 
tion,  316,  318. 

- ,  on  the  age  of  our  oldest  for¬ 
mations,  338. 

- ,  on  alternate  Glacial  periods 

in  the  North  and  South,  396. 

Crosses,  reciprocal,  287. 

Crossing  of  domestic  animals, 
importance  in  altering  breeds, 
18. 

- ,  advantages  of,  90. 

- ,  unfavorable  to  selection,  94. 

Criiger,  Dr.,  on  Coryanthes,  183. 

Crustacea  of  New  Zealand,  399. 

Crustacean,  blind,  131. 

- air-breathers,  181. 

Crustaceans,  their  chelae,  228. 

Cryptocerus,  272. 

Ctenomys,  blind,  130. 

Cuckoo,  instinct  of,  242,  250. 

Cunningham,  Mr.,  on  the  flight 
of  the  logger-headed  duck,  128. 

Currants,  grafts  of,  290. 

Currents  of  sea,  rate  of,  384. 

Cuvier,  on  conditions  of  existence, 
242. 

- ,  Fred.,  on  instinct,  242. 


Cuvier,  on  fossil  monkeys,  335. 
Cyclostoma,  resisting  salt  water, 
417. 

Dana,  Prof.,  on  blind  cave-ani¬ 
mals,  132. 

- ,  on  relations  of  crustaceans 

of  Japan,  395. 

- ,  on  crustaceans  of  New 

Zealand,  399. 

Dawson,  Dr.,  on  eozoon,  339. 

De  Candolle,  Aug.  Pyr.,  on  strug¬ 
gle  for  existence,  58. 

- ,  on  umbelliferae,  138. 

- ,  on  general  affinities,  447. 

De  Candolle,  Alph.,  on  the  varia¬ 
bility  of  oaks,  47. 

- ,  on  low  plants,  widely  dis¬ 
persed,  423. 

- ,  on  widely-ranging  plants 

being  variable,  50. 

- ,  on  naturalization,  105. 

- ,  on  winged  seeds,  139. 

- ,  on  Alpine  species  suddenly 

becoming  rare,  160. 

- ,  on  distribution  of  plants 

with  large  seeds,  385. 

- ,  on  vegetation  of  Australia, 

401. 

- ,  on  fresh-water  plants,  407. 

- ,  on  insular  plants,  410.  J 

Degradation  of  rocks,  315. 
Denudation,  rate  of,  316. 

- of  oldest  rocks,  339. 

- of  granite  areas,  324. 

Development  of  ancient  forms, 
363. 

Devonian  system,  361. 

Dianthus,  fertility  of  crosses,  285 
Dimorphism  in  plants,  42,  297. 
Dirt  on  feet  of  birds,  387. 
Dispersal,  means  of,  381. 

- during  Glacial  period,  389. 

Distribution,  geographical,  373. 

- ,  means  of,  381. 

Disuse,  effect  of,  under  nature, 
128. 

Diversification  of  means  for  same 
general  purpose,  182. 

Division,  physiological,  of  labor 
105. 


INDEX.  525 


Divergence  of  character,  101. 

Dog,  resemblance  of  jaw  to  that 
of  the  Thylacinus,  441. 

Dogs,  hairless,  with  imperfect 
teeth,  11. 

- - descended  from  several  wild 

stocks,  17. 

- ,  domestic  instincts  of,  248. 

- ,  inherited  civilization  of, 

248. 

- ,  fertility  of  breeds  together, 

283. 

- , - of  crosses,  802. 

- ,  proportions  of  body  in  dif¬ 
ferent  breeds,  when  young, 
461. 

Domestication,  variation  under,  6. 
Double  flowers,  271. 

Downing,  Mr  ,  on  fmit-trees  in 
America,  78. 

Dragon  flies,  intestines  of,  175. 
Drift-timber,  885. 

Driver-ant,  274. 

Drones  killed  by  other  bees,  194. 
Duck,  domestic,  wings  of,  re¬ 
duced,  10. 

- ,  beak  of,  217. 

- ,  logger  headed,  166. 

Duckweed,  407. 

Dugong,  affinities  of,  481. 
Dung-beetles  with  deficient  tarsi, 
129. 

Dytiscus,  407. 

Earl,  Mr.  W.,  on  the  Malay 
Archipelago.  415. 

Ears,  drooping,  in  domestic  ani¬ 
mals,  10. 

- ,  rudimentary,  472. 

Earth,  seeds  in  roots  of  trees,  885. 

- charged  with  seeds,  387. 

Echinodermata, their  pedicellari®, 
225. 

Eciton,  272. 

Economy  of  organization,  139. 
Edentata,  teeth  and  hair,  137. 

— — ,  fossil  species  of,  492! 
Edwards,  Milne,  on  physiological 
division  of  labor,  105. 

- ,  on  gradations  of  structure, 

185 


Edwards,  on  embryological  char¬ 
acters,  434. 

Eggs,  young  birds  escaping  from, 
80. 

Egypt,  productions  of,  not  modi¬ 
fied,  200. 

Electric  organs,  178. 

Elephant,  rate  of  increase,  60. 

- ,  of  Glacial  period,  135. 

Embryology,  455. 

Eozoon  Canadense,  339. 

Epilepsy  inherited,  128. 

Existence,  struggle  for,  57. 

- - ,  condition  of,  198. 

Extinction,  as  bearing  on  natural 
selection,  115. 

— — ,  of  domestic  varieties,  111 
- ,  347. 

Eye,  structure  of,  171. 

Eye,  correction  for  aberration, 
194. 

Eyes,  reduced,  in  moles,  130. 

Fabre,  M.,  on  hymenoptera  fight¬ 
ing,  82. 

- ,  on  parasitic  sphex,  255. 

- ,  on  Sitaris,  465. 

Falconer,  Dr.,  on  naturalization 
of  plants  in  India,  61. 

— ■  -  on  elephants  and  mastodons, 
861. 

- and  Cautley,  on  mammals  of 

sub-Himalayan  beds,  368. 
Falkland  Islands,  wolf  of,  414. 
Faults,  817. 

Faunas,  marine,  374. 

Fear,  instinctive,  in  birds,  249. 
Feet  of  birds,  young  molluscs  ad¬ 
hering  to,  407. 

Fertilization  variously  effected, 
183,  191. 

Fertility  of  hybrids,  280. 

- ,  from  slight  changes  in  con¬ 
ditions,  296. 

- of  crossed  varieties,  301. 

Fir-trees  destroyed  by  cattle,  67, 
— — ,  pollen  of,  195. 

Fish,  flying,  166. 

- ,  teleostean,  sudden  appear¬ 
ance  of,  336. 

- eating  seeds-  886,  408- 


520 


INDEX . 


Fish,  fresh- water,  distribution  of, 
406. 

Fishes,  ganoid,  now  confined  to 
fresh  water,  98. 

- ,  electric  organs  of,  178. 

- ,  ganoid,  living  in  fresh 

water,  351. 

- ,  of  southern  hemisphere, 

399. 

Flat-fish,  their  structure,  220. 
Flight,  powers  of,  how  acquired, 
166. 

Flint-tools,  proving  antiquity  of 

man,  16. 

Flower,  Prof.,  on  the  Larnyx, 

225. 

- ,  on  Halitherium,  357. 

• - on  the  resemblance  between 

the  jaws  of  the  dog  and  Tliyla- 
cinus,  441. 

Flower,  Prof.,  on  the  homology 
of  the  feet  of  certain  mar¬ 
supials,  451. 

Flowers,  structure  of,  in  relation 
to  crossing,  86. 

- ,  of  composite  and  umbelli- 

ferae,  137,  205. 

- ,  beauty  of,  191. 

■ - ,  double,  271. 

Flysch  formation,  destitute  of  or¬ 
ganic  remains,  320. 

Forbes,  Mr.  D.,  on  glacial  action 
in  the  Andes,  396. 

- ,  E.,  on  colors  of  shells,  127. 

- ,  on  abrupt  range  of  shells  in 

depth,  161. 

- - ,  on  poorness  of  palaeonto¬ 
logical  collections,  319. 

- ,  on  continuous  succession  of 

genera,  346. 

— — ,  on  continental  extensions, 
382,  383. 

- - ,  on  distribution  during  Gla¬ 
cial  period,  390. 

- - ,  on  parallelism  in  time  and 

space,  426. 

Forests,  changes  in,  in  America, 
69. 

Formation,  Devonian,  361. 

- ,  Cambrian,  339. 

— — ,  intermittent,  328, 


Formations,  thickness  of,  in 
Britain,  317. 

Formica  rufescens,  255. 

- ,  sanguinea,  256. 

- ,  tiava,  neuter  of,  273.  j 

Forms,  lowly  organized,  long  en 
during,  118. 

Frena,  ovigerous,  of  cirri  pedes, 
176 

Fresh- water  productions,  dis¬ 
persal  of,  405. 

Fries,  on  species  in  large  genera 
being  closely  allied  to  othei 
species,  54. 

Frigate-bird,  169. 

Frogs  on  islands,  413. 

Fruit-trees,  gradual  improvement 
of,  31. 

- in  United  States,  48. 

- ,  varieties  of,  acclimatized  in 

United  States,  135. 

Fuci,  crossed,  287,  293. 

Fur,  thicker  in  cold  climates,  127. 

Furze,  457. 

Galapagos  Archipelago,  birds  of, 
411. 

- productions  of,  417,  419. 

Galaxias,  its  wide  range,  406. 

Galeopithecus,  165. 

Game,  increase  of,  checked  by 
vermin,  65. 

Gartner,  on  sterility  of  hybrids, 
279,  280,  284. 

- ,  on  reciprocal  crosses,  286. 

- ,  on  crossed  maize  and  ver- 

bascum,  304. 

- ,  on  comparison  of  hybrids 

and  mongrels,  306,  307. 

Gaudry,  Prof.,  on  intermediate 
genera  of  fossil  mammals  in 
Attica,  357. 

Geese,  fertility  when  crossed,  283. 

- ,  upland,  169. 

Geikie.  Mr.,  on  subaerial  denuda¬ 
tion,  316. 

Genealogy,  important  in  classifi¬ 
cation,  435. 

Generations,  alternate,  456. 

Geographical  distribution,  373. 

Geography,  ancient,  503. 


INDEX. 


52? 


Geoffroy  St.  Hilaire.  on  balance- 
ment,  139= 

- ;  on  homologous  organs.  451. 

- .  Isidore,  on  variability  of  re 

peated  parts  140. 

- or  correlation,  in  monstrosi¬ 
ties,  10 

- ,  on  correlation  137. 

- ,  on  variable  parts  being 

often  monstrous,  145. 

Geology,  future  progress  of,  502. 

- ,  imperfection  of  the  record, 

503. 

Gervais,  Prof.,  on  Typotherium, 
357. 

Giraffe,  tail  of,  186. 

- ,  structure  of,  209. 

Glacial  period,  389. 

- ,  affecting  the  North  and 

South,  395. 

Glands,  mammary,  224. 

Gmelin,  on  distribution,  390 
Godwin- Austen,  Mr.,  on  the 
Malay  Archipelago,  331. 

Goethe,  on  compensation  of 
growth,  139. 

Gomphia,  207. 

Gooseberry,  grafts  of,  290. 

Gould,  Dr.  Aug.  A.,  on  land- 
shells,  416. 

- ,  Mr,,  on  colors  of  birds,  127. 

- ,  on  instincts  of  cuckoo,  253. 

- ,  on  distribution  of  genera  of 

birds,  422. 

Gourds,  crossed,  304. 

Graba,  on  the  Uria  lacrymas,  85. 
Grafting,  capacity  of,  289,  290. 
Granite,  areas  of  denuded,  324. 
Grasses,  varieties  of,  103, 

Gray,  Dr.  Asa,  on  the  variability 
of  oaks,  47. 

■ - ,  on  man  not  causing  varia¬ 

bility,  73. 

- ,  on  sexes  of  the  holly,  87. 

- ,  on  trees  of  the  United 

States,  93. 

- ,  on  naturalized  plants  in  the 

United  States,  105. 

- ,  on  aestivation,  206. 

- ,  on  rarity  of  intermediate  va¬ 
rieties,  162 


Gray,  on  Alpine  plants,  390. 

- ,  Dr.  J.  E.,  on  striped  mule^ 

152. 

Grebe,  169 

Grimm,  on  asexual  reproduction, 
456. 

Groups,  aberrant,  446. 

Grouse,  colors  of,  78. 

~ — >  red,  a  doubtful  species,  45. 
Growth,  compensation  of,  139. 
Gunther,  Dr.,  on  flat-fish,  222. 

- ,  on  prehensile  tails,  223. 

- ,  on  the  fishes  of  Panama, 

374. 

• - >  on  the  range  of  fresh- water 

fishes,  406. 

- ,  on  the  limbs  of  Lepidosiren, 

470. 

Haast,  Dr.,  on  glaciers  of  New 
Zealand,  395. 

Habit,  effect  of,  under  domes¬ 
tication,  10. 

- ; ,  effect,  of,  under  nature,  129. 

Habit,  diversified, of  same  species, 
167. 

Hackel,  Prof.,  on  classification 
and  the  lines  of  descent,  450. 
Hair  and  teeth,  correlated,  137. 
Halitherium,  357. 

Harcourt,  Mr.  E.  V.,  on  the  birds 
of  Madeira,  411. 

Hartung,  M.,  on  bowlders  in  the 
Azores,  388. 

Hazel-nuts,  384. 

Hearne,  on  habits  of  bears,  168. 
Heath,  changes  in  vegetation,  66. 
Hector,  Dr.,  on  glaciers  of  New 
Zealand,  395. 

Heer,  Oswald,  on  ancient  culti¬ 
vated  plants,  16. 

- on  plants  of  Madeira,  98. 

Helianthemum,  207. 

Helix  pomatia,  417. 

— — ,  resisting  salt  water,  417. 
Helmholtz,  M.,  on  the  imperfeo- 
tion  of  the  human  eye,  194. 
Helosciadium,  384. 

Hemionus,  striped,  154. 

Hensen,  Dr.,  on  the  eyes  of 
Cephalopoda,  180. 


52S 


INDEX. 


Herbert  W.,  on  straggle  for  exist¬ 
ence,  58. 

- ,  on  sterility  of  hybrids,  281. 

Hermaphrodites  crossing,  90. 

Heron  eating  seed,  409. 

Heron,  Sir  R.,  on  peacocks,  82. 

Heusinger,  on  white  animals  poi¬ 
soned  by  certain  plants,  11. 

Hewitt,  Mr.,  on  sterility  of  first 
crosses,  293. 

Hildebrand,  Prof.,  on  the  self- 
sterility  of  Corydalis,  281. 

Hilgendorf,  on  intermediate  varie¬ 
ties,  325. 

Himalaya,  glaciers  of,  395. 

- ,  plants  of,  398. 

Hippeastrnm,  281. 

Hippocampus,  224. 

Hofmeister,  Prof.,  on  the  move¬ 
ments  of  plants,  234. 

Holly-trees,  sexes  of,  87. 

Hooker,  Dr.,  on  trees  of  New 
Zealand,  93. 

- ,  on  acclimatization  of  Hima¬ 
layan  trees,  134. 

Hooker,  Dr.,  on  flowers  of  um- 
belliferae,  138. 

- ,  on  the  position  of  ovules, 

204. 

— — ,  on  glaciers  of  Himalaya, 
395. 

- ,  on  algae  of  New  Zealand, 

399. 

- ,  on  vegetation  at  the  base  of 

the  Hymalaya,  399. 

- ,  on  plants  of  Tierra  del 

Fuego,  397. 

- - ,  on  Australian  plants,  398, 

'419. 

- - ,  on  relations  of  flora  of 

America,  401. 

■ - ,  on  flora  of  the  Antarctic 

lands,  403,  418. 

- ,  on  the  plants  of  the  Gala¬ 
pagos,  412,  417. 

- .  on  glaciers  of  the  Lebanon, 

395. 

- ,  on  man  not  causing  varia¬ 
bility,  73, 

- ,  on  plants  of  mountains  of 

Fernando,  Po,  398. 


Hooks  on  palms,  188. 

- on  seeds,  on  islands,  413. 

Hopkins,  Mr.,  on  denudation, 

323. 

Hornbill,  remarkable  instinct  of, 
276. 

Horns,  rudimentary,  472. 

Horse,  fossil,  in  La  Plata,  348. 

- ,  proportions  of,  when  young 

462. 

Horses  destroyed  by  flies  in  Para, 
guay,  67. 

- ,  striped,  152. 

Horticulturists,  selection  applied 
by,  28. 

Huber,  on  cells  of  bees,  264. 

— — ,  P.,  on  reason  blended  with 
instinct,  242. 

- ,  on  habitual  nature  of  in¬ 
stincts,  243. 

- ,  on  slave-making  ants,  255. 

- ,  on  Melipona  domestica,  260. 

Hudson,  Mr.,  on  the  Ground- 
Woodpecker  of  La  Plata,  168. 

- ,  on  the  Molothrus,  253. 

Humble-bees,  cells  of,  260. 
Hunter,  J.,  on  secondary  sexual 
characters,  142. 

Hutton,  Captain,  on  crossed 
geese,  283. 

Huxley,  Prof.,  on  structure  of 
hermaphrodites,  93. 

- ,  on  the  affinities  of  the 

Sirenia,  357. 

- ,  on  forms  connecting  birds 

and  reptiles,  357. 

- ,  on  homologous  organs,  455. 

- ,  on  the  development  oi 

aphis,  460. 

Hvbrids  and  mongrels  compared, 
305. 

Hybridism,  277. 

Hydra,  structure  of,  175. 
Hymenoptera,  fighting,  82. 
Hymenopterous  insect,  diving 
169. 

Hyoseris,  205. 

Ibla,  140. 

Icebergs  transporting  seeds,  38? 
Increase,  rate  of,  60. 


INDEX .  529 


Individuals,  numbers  favorable  to 
selection,  94. 

- ,  many,  whether  simulta¬ 
neously  created,  380. 
Inheritance,  laws  of,  12. 

- ,  at  corresponding  ages,  12. 

Insects,  color  of,  fitted  for  their 
stations,  78. 

- ,  sea  side,  colors  of,  127. 

- ,  blind,  in  caves..  131. 

- - ,  luminous,  180. 

- their  resemblance  to  certain 

objects,  214. 

- ,  neuter,  272. 

Instinct,  242. 

- .  not  varying  simultaneously 

with  structure,  270. 

Instincts,  domestic,  247. 
Intercrossing,  advantages  of,  90, 
296. 

Islands,  oceanic,  409. 

Isolation  favorable  to  selection, 
96. 

Japan,  productions  of,  395. 

Java,  plants  of,  398. 

Jones,  Mr.  J.  M.,  on  the  birds  of 
Bermuda,  411. 

Jourdain,  M.,  on  the  eye- spots  of 
star  fishes,  171. 

Jukes,  Prof.,  on  subaerial  denu¬ 
dation,  316. 

Jussieu,  on  classification,  433. 

Kentucky,  caves  of,  101. 
Kerguelen-land,  flora  of,  403,  418. 
Kidney-bean,  acclimatization  of, 
135. 

Kidneys  of  birds,  137 J 
Kirby,  on  tarsi  deficient  in  bee¬ 
tles,  129. 

Knight,  Andrew,  on  cause  of 
variation,  6. 

Kolreuter,  on  intercrossing,  89. 

- ,  on  the  barberry,  91. 

- ,  on  sterility  of  hybrids,  278, 

281. 

- - ,  on  crossed  varieties  of  nico 

tiana,  305. 

• - ,  on  crossing  male  and  herma¬ 

phrodite  flowers,  468. 


Kolreuter,  on  reciprocal  crosses, 
287 

Lamarck,  on  adaptive  characters, 
440. 

Lancelet,  118. 

- ,  eyes  of,  173. 

Landois,  on  the  development  of 
the  wings  of  insects,  176. 
Land-shells,  distribution  of.  416. 

- ,  of  Madeira,  naturalized,  421. 

- ,  resisting  salt  water,  417. 

Languages,  classification  of,  437. 
Lankester,  Mr.  E.  Ray,  on  Longe¬ 
vity,  200. 

- ,  on  homologies,  454. 

Lapse,  great,  of  time,  314. 

Larvae,  457,  458,  459. 

Laurel,  nectar  secreted  by  the 
leaves,  86. 

Laurentian  formation,  339. 

Laws  of  variation,  126. 

Leech,  varieties  of,  70. 
Leguminosae,  nectar  secreted  by 
glands,  86, 

Leibnitz’  attack  on  Newton,  496. 
Lepidosiren,  98,  358. 

- ,  limbs  in  a  nascent  condition, 

470. 

Lewes,  Mr.  G.  H.,  on  species  not 
having  changed  in  Egypt,  200. 

- ,  on  the  Salamandra  atra, 

468. 

- ,  on  many  forms  of  life  hav¬ 
ing  been  at  first  evolved,  500. 
Life,  struggle  for,  58. 

Lingula,  Silurian,  338. 

Linnaeus,  aphorism  of,  430, 

Lion,  mane  of,  82. 

- ,  young  of,  striped,  457. 

Lobelia  fulgens,  68,  91. 

- ,  sterility  of  crosses,  281. 

Lockwood,  Mr.,  on  the  ova  of  the 
Hippocampus,  224. 

Locusts  transporting  seeds,  386. 
Logan,  Sir  W.,  on  Laurentian 
formation,  339. 

Lowness  of  structure  connected 
with  variability,  140. 

- ,  related  to  wide  distribution, 

423. 


530 


INDEX. 


Lowe,  Rev.  R.  T.,  on  locusts 
visiting  Madeira,  386, 

Lubbock,  Sir  J.,  on  tbe  nerves  of 
coccus,  41. 

- ,  on  secondary  sexual  charac¬ 
ters,  147. 

- ,  on  a  diving  kymenopterous 

insect,  169. 

- — on  affinities,  331. 

- - ;  on  metamorphoses,  455,  458. 

Lucas,  Dr.  P.,  on  inheritance,  11. 

- ,  on  resemblance  of  child  to 

parent,  308. 

Lund  and  Clausen,  on  fossils  of 
Brazil,  367. 

Lyell,  Sir  C.,  on  the  struggle  for 
existence,  58. 

- ,  on  modern  changes  of  the 

earth,  89. 

- ,  on  terrestrial  animals  not 

having  been  developed  on  isl¬ 
ands,  213. 

- ,on  a  carboniferous  land-shell, 

320. 

- ,  on  strata  beneath  Silurian 

system,  386. 

- ,  on  the  imperfection  of  the 

geological  record,  342. 

- ,  on  the  appearance  of 

species,  342. 

- - ,  on  Barrande’s  colonies,  344. 

- ,  on  tertiary  formations  of 

Europe  and  North  America,  352. 

- - ,  on  parallelism  of  tertiary 

formations,  356. 

— — ,  on  transport  of  seeds  by 
icebergs,  388. 

- — — ,  on  great  alterations  of  cli¬ 
mate,  404. 

- - ,  on  the  distribution  of  fresh¬ 
water  shells,  407. 

— — ,  on  land-shells  of  Madeira, 
421. 

Lyell  and  Dawson,  on  fossilized 
trees  in  Nova  Scotia,  328. 
Lythrum  salicaria,  trimorphic, 
300. 

Macleay,  on  analogical  characters, 
440. 

Macrauchenia  357. 


M’Donnell,  Dr.,  on  electric  organs, 
178. 

Madeira,  plants  of,  98. 

- ,  beetles  of,  wingless,  129. 

- ,  fossil  land-shells  of,  367 

- ,  birds  of,  411. 

Magpie  tame  in  Norway,  246. 
Males  fighting,  81. 

Maize,  crossed,  304. 

Malay  Archipelago  compared  with 
Europe,  331. 

- ,  mammals  of,  415. 

Malm,  on  flat-fish,  221. 
Malpighiaceae,  small  imperfect 
flowers  of,  204. 

- ,  433. 

Mammae,  their  development,  224. 

- ,  rudimentary,  467. 

Mammals,  fossil,  in  secondary 
formation,  335. 

- ,  insular,  414. 

Man,  origin  of,  504. 

Manatee,  rudimentary  nails  of, 
471. 

Marsupials  of  Australia,  106. 

- ,  structure  of  their  feet,  450. 

Marsupials,  fossil  species  of,  367 
Martens,  M.,  experiment  on  seeds, 
384. 

Martin,  Mr.  W.  C.,  on  striped 
mules,  153. 

Masters,  Dr.,  on  Saponaria,  207. 
Matteu cci,  on  the  electric  organs 
of  rays,  178. 

Matthiola,  reciprocal  crosses  of, 
287. 

Maurandia,  232. 

Means  of  dispersal,  381. 

Melipona  domestica,  260. 

Merrill,  Dr.,  on  the  American 
cuckoo,  251. 

Metamorphism  of  oldest  rocks. 
339. 

Mice  destroying  bees,  68. 

- ,  acclimatization  of,  134. 

- ,  tails  of,  223. 

Miller,  Prof.,  on  the  cells  of  bees, 
261,  265. 

Mirabilis,  crosses  of,  287. 

Missel-thrush,  70 

Mistletoe,  complex  relations  of,  3 


INDEX, 


Mivart,  Mr.,  on  tlie  relation  of 
hair  and  teeth,  137, 

- ,  on  the  eyes  of  cephalopoas. 

180. 

- ,  various  objections  to  Natu 

ral  Selection,  209. 

- ,  on  abrupt  modifications, 

237. 

- ,  on  the  resemblance  of  the 

mouse  and  antechinus,  440. 
Mocking-thrush  of  the  Galapagos, 
421 . 

Modification  of  species  not  abrupt, 
499. 

Moles,  blind,  130. 

Molothrus,  habits  of,  253. 
Mongrels,  fertility  and  sterility  of, 
301. 

- and  hybrids  compared,  305. 

Monkeys,  fossil,  355. 
Monachanthus,  438. 

Mons,  Van,  on  the  origin  of  fruit 
trees,  25. 

Monstrosities,  39. 

Moquin  -  Tandon,  on  sea  -  side 
plants,  127. 

Morphology,  450. 

Morren,  on  the  leaves  of  Oxalis, 
233 

Moths,  hybrid,  283. 

Mozart,  musical  powers  of,  243. 
Mud.  seeds  in,  408. 

Mules,  striped,  153. 

Muller,  Adolph,  on  the  instincts 
of  the  cuckoo,  251. 

Muller,  Dr.  Ferdinand,  on  Alpine 
Australian  plants,  398. 

Muller,  Fritz,  on  dimorphic  crus¬ 
taceans,  42,  274. 

- - ,  on  the  lancelet,  119. 

- ,  on  air-breathing  crusta¬ 
ceans,  181. 

- - ,  on  the  self- sterility  of 

orchids,  281. 

- ,  on  embryology  in  relation 

to  classification,  434. 

- ,  on  the  metamorphoses  of 

crustaceans,  460,  466. 

- ,  on  terrestrial  and  fresh¬ 
water  organisms  not  under¬ 
going  any  metamorphosis,  464.  | 


531 

MiiIIei>,  Fritz,  on  climbing  plants, 
233. 

Multiplication  of  species  not  in¬ 
definite,  121. 

Murchison,  Sir  R.,  on  the  forma 
tions  of  Russia,  321. 

- -,  on  azoic  formations,  339. 

- ,  on  extinction,  347. 

Murie,  Dr.,  on  the  modification  of 
the  skull  in  old  age,  177. 
Murray,  Mr.  A.,  on  cave-insects, 
132. 

Mustela,  vision,  164. 

Myanthus,  438. 

Myrmecocystus,  272. 

Myrmica,  eyes  of,  273. 

Nageli,  on  morphological  charac' 
ters,  202. 

Nails,  rudimentary.  471. 
Nathusius,  Von,  on  pigs,  189. 
Natural  history,  future  progress 
of,  502. 

- ,  selection,  73. 

- ,  system,  430. 

Naturalization  of  forms  distinct 
from  the  indigenous  species, 
105. 

Naturalization  in  New  Zealand, 
193. 

Naudin,  on  analogous  variations 
in  gourds,  149. 

- -,  on  hybrid  gourds,  304. 

Naudin,  on  reversion,  307. 
Nautilus,  Silurian,  338. 

Nectar  of  plants,  86. 

Nectaries,  how  formed,  86. 
Nelumbium  luteum,  409. 

Nests,  variations  in,  246,  269,  275 
Neuter  insects,  272,  273. 

Newman,  Col.,  on  humble-bees, 

68. 

New  Zealand,  productions  of,  not 
perfect,  193. 

- ,  naturalized  products  of,  366. 

- ,  fossil  birds  of,  367. 

- ,  glaciers  of,  395. 

- ,  crustaceans  of,  399. 

- ,  algae  of  399. 

- ,  number  of  plants  of,  410. 

- ,  flora  of,  419. 


532 


INDEX. 


Newton,  Sir  I.,  attacked  for  irre- 
ligion,  496. 

- ,  Prof.,  on  eartli  attached  to 

a  partridge’s  foot,  387. 
Nicotiana,  crossed  varieties  of, 
305. 

• - ,  certain  species  very  sterile, 

286. 

Nitsche,  Dr.,  on  the  Polyzoa, 
228. 

Noble,  Mr.,  on  fertility  of  Rhodo¬ 
dendron,  282. 

Nodules,  phosphatic,  in  azoic 
rocks,  339. 

Oaks,  variability  of,  47. 

Onites,  appelles,  129, 

Ononis,  small  imperfect  flowers 
of,  204. 

Orchids,  fertilization  of,  183. 

- ,  the  development  of  their 

flowers,  230. 

- ,  forms  of,  438. 

Orchis,  pollen  of,  180. 
Organization,  tendency  to  ad¬ 
vance,  116. 

Organs  of  extreme  perfection,  170, 

- ,  electric,  of  fishes,  178. 

- ,  of  little  importance,  186. 

- ,  homologous,  451. 

- ,  rudiments  of,  and  nascent, 

467. 

Ornithorhynchus,  98,  432. 

- ,  mammae  of,  224. 

Ostrich  not  capable  of  flight,  213. 
- ,  habit  of  laying  eggs  to¬ 
gether,  255. 

- ,  American,  two  species  of, 

375. 

Otter,  habits  of,  how  acquired, 
164. 

Ouzel,  water,  169. 

Owen,  Prof.,  on  birds  not  flying, 
128. 

- ,  on  vegetative  repetition, 

141. 

- ,  on  variability  of  unusually 

developed  parts,  141. 

- ,  on  the  eyes  of  fishes.  173 

- ,  on  the  swim-bladder  of 

fishes,  176. 


Owen,  Prof.,  on  fossil  horse  of  La 
Plata,  348. 

- ,  on  generalized  form,  357. 

- ,  on  relation  of  ruminants 

and  pachyderms,  357. 

- ,  on  fossil  birds  of  New  Zea¬ 
land,  367. 

- ,  on  succession  of  types,  367 

- ,  on  affinities  of  the  dugong, 

431. 

- ,  on  homologous  organs,  451. 

- ,  on  the  metamorphosis  of  ce- 

phalopods,  459. 

Pacific  Ocean,  faunas  of,  375. 
Pacini,  on  electic  organs,  179. 
Paley,  on  no  organ  formed  to  give 
pain,  193. 

Pallas,  on  the  fertility  of  the 
domesticated  descendants  of 
wild  stocks,  284. 

Palm  with  hooks,  188. 

Papaper  bracteatum,  206. 
Paraguay,  cattle  destroyed  by 
flies,  67. 

Parasites,  253. 

Partridge,  with  ball  of  earth  at¬ 
tached  to  foot,  287. 

Parts  greatly  developed,  variable, 
141. 

Parus  major,  168. 

Passiflora,  281. 

Peaches  in  United  States,  78. 
Pear,  grafts  of,  290. 

Pedicellarise,  226. 

Pelagornium,  flowers  of,  138. 

- ,  sterility  of,  282. 

Pelvis  of  women,  137. 

Peloria,  138. 

Period,  glacial,  389. 

Petrels,  habits  of,  169. 

Phasianus,  fertility  of  hybrids, 
283. 

Pheasant,  young,  wild,  249. 

Pictet,  Prof.,  on  groups  of  spe¬ 
cies  suddenly  appearing,  333. 

- ,  on  rate  of  organic  change, 

344. 

- •.  on  continuous  succession  of 

genera,  346. 


INDEX.  533 


Pictet.  Prof.,  on  close  alliance  of 
fossils  in  consecutivet'ormations, 
362. 

- ,  on  change  in  latest  tertiary 

forms,  329. 

- ,  on  early  transitional  links, 

334. 

Pierce,  Mr. ,  on  varieties  of  wolves, 
83. 

Pigeons  with  feathered  feet  and 
skin  between  toes,  11. 

- ,  breeds  described,  and  origin 

of,  18. 

- ,  breeds  of,  how  produced, 

33,  35. 

- ,  tumbler,  not  being  able  to 

get  out  of  egg.  80. 

- ,  reverting  to  blue  color,  151. 

- ,  instinct  of  tumbling,  248. 

- ,  young  of,  462. 

Pigs,  black,  not  affected  by  the 
paint-root,  11. 

- ,  modified  by  want  of  exer¬ 
cise,  189. 

Pistil,  rudimentary,  468. 

Plants,  poisonous,  not  affecting 
certain  colored  animals,  11. 

- ,  selection,  applied  to,  31. 

- ,  gradual  improvement  of,  31. 

- ,  not  improved  in  barbarous 

countries,  32. 

- ,  dimorphic,  42,  297. 

- ,  destroyed  by  insects,  63. 

- ,  in  midst  of  range,  have  to 

struggle  with  other  plants,  71. 

- ,  nectar  of,  86. 

- ,  fleshy,  on  sea-shores,  127. 

- ,  climbing,  175,  232. 

- ,  fresh- water,  distribution  of, 

407. 

- ,  low  in  scale,  widely  dis¬ 
tributed,  423. 

Pleuronectidae,  their  structure, 
220. 

Plumage,  laws  of  changes  in 
sexes  of  birds,  82. 

Plums  in  the  United  States.  78. 
Pointer  dog,  origin  of,  3C. 

- ,  habits  of,  248. 

Poison  not  affecting  certain 
colored  animals,  11. 


Poison,  similar  effect  of,  on  ani¬ 
mals  and  plants,  500. 

Pollen  of  fir-trees,  195. 

-  transported  by  various 

means,  183,  191. 

Pollinia,  their  development,  230. 

Polyzoa,  their  avicularia,  228. 

Poole,  Col.,  on  striped  hemionus, 
154. 

Potemogeton,  408. 

Pouchet,  on  the  colors  of  flat-fish, 

222. 

Prestwich,  Mr.,  on  English  and 
French  eocene  formations,  355. 

Proctotrupes,  169. 

Proteolepas,  140. 

Proteus,  133. 

Psychologv,  future  progress  of, 
504. 

Pyrgoma,  found  in  the  chalk, 
336. 

Quagga,  striped,  154. 

Quatrefages,  M.,  on  hybrid  moths, 
283. 

Quercus,  variability  of,  48. 

Quince,  grafts  of,  290. 

Rabbits,  disposition  of  young, 
249. 

Races,  domestic,  characters  of,  14. 

Race-horses,  Arab,  30. 

- ,  English,  381. 

Radcliffe,  Dr.,  the  electrical  or¬ 
gans  of  the  torpedo,  178. 

Ramond,  on  plants  of  Pyrenees, 
391. 

Ramsay,  Prof. ,  on  subaerial  denu¬ 
dation,  316. 

- ,  on  thickness  of  the  British 

formations,  317. 

- ,  on  faults,  317. 

Ramsay,  Mr.,  on  instincts  of 
cuckoo,  252. 

Ratio  of  increase,  60. 

Rats  supplanting  each  other,  70. 

- ,  acclimatization  of,  134. 

- ,  blind,  in  cave,  131. 

Rattle-snake,  192. 

Reason  and  instinct.  242. 
Recapitulation,  general,  476. 


534 


INDEX. 


Reciprocity  of  crosses,  287. 

Record,  geological,  imperfect,  312. 

Rengger,  on  dies  destroying  cat¬ 
tle,  6-7. 

Reproduction,  rate  of,  60. 

Resemblance,  protective,  of  in¬ 
sects,  215. 

- to  parents  in  mongrels  and 

hybrids,  306. 

Reversion,  law  of  inheritance,  13. 

- ,  in  pigeons,  to  blue  color, 

151. 

Rhododendron,  sterility  of,  282. 

Richard,  Prof.,  on  Aspicarps,  433. 

Richardson,  Sir  J.,  on  structure 
of  squirrels,  165. 

- ,  on  fishes  of  the  southern 

hemisphere,  399. 

Robinia,  grafts  of,  290. 

Rodents,  blind,  130. 

Rogers,  Prof.,  Map  of  N,  America, 
324. 

Rudimentary  organs,  467. 

Rudiments  important  for  classi¬ 
fication,  432. 

Riitimeyer,  on  Indian  cattle,  16, 
284. 

Salamandre  atra,  468. 

Saliva  used  in  nests,  269. 

Salvin,  Mr.,  on  the  beaks  of 
ducks,  218. 

Sageret,  on  grafts,  290. 

Salmons,  males  fighting,  and 
hooked  jaws  of,  81. 

Salt  water,  how  far  injurious  to 
seeds,  383. 

- not  destructive  to  land-shells, 

^  417. 

Salter,  Mr.,  on  early  death  of 
hybrid  embryos,  293. 

Saurophagus  sulphuratus,  168. 

Schacht,  Prof.,  on  Phyllotaxy, 
205. 

Schiodte,  on  blind  insects,  131. 

- ,  on  flat-fish,  220. 

Schlegel,  on  snakes,  137. 

Schobl,  Dr.,  on  the  ears  of  mice, 
203. 

Scott,  J.,  Mr.,  on  the  self-sterility 
of  orchids,  281. 


Scott,  J.,  Mr.,  on  the  crossing  of 
varieties  of  verbascum,  304. 
Sea- water,  how  far  injurious  to 
seeds,  383. 

- not  destructive  to  land-shells, 

,  417. 

Seabright,  Sir  J.,  on  crossed  ani¬ 
mals,  18. 

Sedgwick,  Prof.,  on  groups  of 
species  suddenly  appearing,  333. 
Seedlings  destroyed  by  insects,  63. 
Seeds,  nutriment  in,  71. 

- ,  winged,  139. 

- ,  means  of  dissemination,  183, 

191,  385. 

— — ,  power  of  resisting  salt 
water,  383. 

- ,  in  crops  and  intestines  of 

birds,  386. 

- ,  eaten  by  fish,  386,  408. 

- ,  in  mud,  408. 

- ,  hooked,  on  islands,  413. 

Selection  of  domestic  products, 
25. 

- ,  principle  not  of  recent  ori¬ 
gin,  29. 

- ,  unconscious,  29. 

- ,  natural,  73. 

- ,  sexual,  81. 

- ,  objections  to  term,  74. 

- natural,  has  not  induced 

sterility,  291. 

Sexes,  relations  of,  81. 

Sexual  characters  variable,  146. 

- ,  selection,  81. 

Sheep,  Merino,  their  selection,  27. 
- ,  two  sub-breeds,  uninten¬ 
tionally  produced,  31. 

- ,  mountain  varieties  of,  70. 

Shells,  colors  of,  127. 

- ,  hinges  of,  182. 

- ,  littoral,  seldom  embedded, 

,  319- 

Shells,  fresh- water,  long  retain 
the  same  forms,  364. 

- ,  fresh-water,  dispersal  of, 

406. 

- ,  of  Madeira,  412. 

- ,  land,  distribution  of,  412. 

- ,  land,  resisting  salt  water, 

417. 


INDEX. 


535 


Shrew-mouse,  440. 

Silene,  infertility  of  crosses,  286. 
Silliman,  Prof.,  on  blind  rat, 
181. 

Sirenia,  tlieir  affinities,  857. 
Sitaris,  metamorphosis  of,  465. 
Skulls  of  young  mammals,  188, 
453. 

Slave-making  instinct,  255. 

Smith,  Col.  Hamilton,  on  striped 
horses,  153. 

■ - ,  Mr.  Fred.,  on  slave-making 

ants,  256. 

- - ,  on  neuter  ants,  273. 

Smith,  Dr. ,  on  the  Polyzoa,  228. 
Snake  with  tooth  for  cutting 
through  egg-shell,  253. 
Somerville,  Lord,  on  selection  of 
sheep,  27. 

Sorbus,  grafts  of,  290. 

Sorex,  440. 

Spaniel,  King  Charles’  breed,  30. 
Specialization  of  organs,  117. 
Species,  polymorphic,  41. 

- ,  dominant,  51. 

- ,  common,  variable,  50. 

- in  large  genera  variable,  52. 

- ,  groups  of,  suddenly  appear¬ 
ing,  333,  337. 

- beneath  Silurian  formations, 

339. 

- successively  appearing,  343. 

-  changing  simultaneously 

throughout  the  world,  352. 
Spencer,  Lord,  on  increase  in  size 
of  cattle,  30. 

- ,  Herbert,  Mr.,  on  the  first 

steps  in  diffentiation,  120. 

- ,  on  the  tendency  to  an 

equilibrium  in  all  forces,  297. 
Sphex,  parasitic,  255. 

Spiders,  development  of,  460. 
Sports  in  plants,  9. 

Sprengel,  C.  C.,  on  crossing,  89. 

- ,  on  ray-florets,  138. 

Squalodon,  357. 

Squirrels,  gradations  in  structure, 
165. 

Staffordshire,  heath,  changes  in, 

66. 

Stag-beetles,  fighting,  81. 


Star  fishes,  eyes  of,  171. 

- ,  their  pedicellariae,  227. 

Sterility  from  changed  conditions 
of  life,  8. 

- of  hybrids,  279. 

- ,  laws  of,  284. 

- ,  causes  of,  291. 

- ,  from  unfavorable  condi¬ 
tions,  295. 

- not  induced  through  natural 

selection,  292. 

St.  Helena,  productions  of,  410. 

St.  Hilaire,  Aug.,  on  variability 
of  certain  plants,  206. 

- ,  on  classification,  433. 

St.  John,  Mr.,  on  habits  of  cats, 
247. 

Sting  of  bee,  194. 

Stocks,  aboriginal,  of  domestic 
animals,  17. 

Strata,  thickness  of,  in  Britain, 
317. 

Stripes  on  horses,  152. 

Structure,  degrees  of  utility  of, 

,  189. 

Struggle  for  existence,  57. 
Succession,  geological,  343. 

- of  types  in  same  areas,  367. 

Swallow,  one  species  supplanting 
another,  70. 

Swaysland,  Mr.,  on  earth  adher¬ 
ing  to  the  feet  of  migratory 
birds,  387. 

Swifts,  nests  of,  269. 
Swim-bladder,  175. 

Switzerland,  lake  inhabitations 
of,  16. 

System,  natural,  430. 

Tail  of  giraffe,  186. 

- of  aquatic  animals,  187. 

- ,  prehensible,  223. 

- ,  rudimentary,  571. 

Tanais,  dimorphic,  42. 

Tarsi,  deficient,  129. 

Tauscli,  Dr.,  on  umbelliferas,  205. 
Teeth  and  hair  correlated,  137. 

- ,  rudimentary,  in  embryonic 

calf,  467,  495. 

Tegetmeier,  Mr.,  on  cells  of  bees, 
262,  267. 


536 


INDEX. 


Temminck,  on  distribution  aiding 
classification,  435. 

Tendrils,  their  development,  282. 
Thompson,  Sir  W.,  on  the  age  of 
the  habitable  wurld,  338 

- ,  on  the  consolidation  of  the 

crust  of  the  earth,  482. 

Thouin,  on  grafts,  290. 

Thrush,  aquatic  species  of,  169. 

- ,  mocking,  of  the  Galapagos, 

421. 

- ,  young  of,  spotted,  457. 

- ,  nest  of,  276. 

Thuret,  M.,  on  crossed  fuci,  287. 
Th  waites,  Mr. ,  on  acclimatization, 
134. 

Thylacinus,  441. 

Tierra  del  Fuego,  dogs  of,  249. 

- ,  plants  of,  403. 

Timber-drift,  385. 

Time,  lapse  of,  314. 

- ,  by  itself  not  causing  modi- 

cation,  95. 

Titmouse,  168. 

Toads  on  islands,  413. 

Tobacco,  crossed  varieties  of,  305. 
Tomes,  Mr.,  on  the  distribution 
of  bats,  415. 

Transitions  in  varieties  rare,  159. 
Traquair,  Dr.,  on  flat-fish,  222. 
Trautschold,  on  intermediate 
varieties,  325. 

Trees  on  islands  belong  to  pecul¬ 
iar  orders,  413. 

- with  separated  sexes,  92. 

Trifolium  pratense,  68,  88. 

- incarnatum,  88. 

Trigonia,  351. 

Trilobites,  338. 

- ,  sudden  extinction  of,  351. 

Trimen,  Mr.,  on  imitating-insects, 
444. 

Trimorphism  in  plants,  42,  297. 
Troglodytes,  276. 

Tuco-tuco-blind,  130. 

Tumbler  pigeons,  habits  of,  he¬ 
reditary,  248. 

Tumbler,  young  of,  462. 
Turkey-cock,  tuft  of  hair  on 
breast,  83. 

c - ,  naked  skin  on  head,  188. 


Turkey-cock,  young  of,  instinct¬ 
ively  wild,  249. 

Turnip  and  cabbage,  analogous 
variations  of,  149. 

Type,  unity  of,  197,  198. 

Types,  succession  of,  in  same 
areas,  367. 

Typotherium,  357. 

Udders  enlarged  by  use,  10. 

- ,  rudimentary,  468. 

Ulex,  young  leaves  of,  457. 
Umbelliferse,  flowers  and  seeds 
of,  138. 

- ,  outer  and  inner  florets  of, 

205. 

Unity  of  type,  197,  198. 

Uria  lacrymans,  85. 

Use,  effects  of,  under  domestica¬ 
tion,  10. 

- ,  effects  of,  in  a  state  of 

nature,  128. 

Utility,  how  far  important  in  the 
construction  of  each  part,  189. 

Valenciennes,  on  fresh-water  fish, 
406. 

Variability  of  mongrels  and 
hybrids,  305. 

Variation,  under  domestication,  7. 

- caused  by  reproductive  sys 

tern  being  affected  by  conditions 
of  life,  8. 

- under  nature,  39. 

- ,  laws  of,  126. 

- ,  correlated,  10,  186,  189. 

Variations  appear  at  correspond¬ 
ing  ages,  12,  79. 

-  analogous  in  distinct  spe¬ 
cies,  148. 

Varieties,  natural,  37. 

- ,  struggle  between,  70. 

- ,  domestic,  extinction  of,  101. 

- ,  transitional,  rarity  of,  159. 

- ,  when  crossed,  fertile,  301. 

Varieties,  when  crossed,  sterile, 
303. 

- ,  classification  of,  437. 

Verbascum,  sterility  of,  281. 

- ,  varieties  of,  crossed,  304. 

Verlot,  M.,  on  doubt**  stocks,  271. 


INDEX.  537 


Verneuil,  M.  de,  on  the  succes¬ 
sion  of  species.  353. 

Vibracula  of  the  Polyzoa,  229. 

Viola,  small  imperfect  flowers  of, 
204. 

- ,  tricolor,  68. 

Virchow,  on  the  structure  of  the 
crystalline  lens,  173. 

Virginia,  pigs  of,  78. 

Volcanic  islands,  denudation  of, 
316. 

Vulture,  naked  skin  on  head,  188. 

Wading-birds,  408. 

Wagner,  Dr.,  on  Cecidomyia,  456. 

Wagner,  Moritz,  on  the  import¬ 
ance  of  isolation,  96. 

Wallace,  Mr.,  on  origin  of  spe¬ 
cies,  1. 

- ,  on  the  limit  of  variation 

under  domestication,  36. 

- ,  on  dimorphic  lepidoptera, 

42,  274. 

- ,  on  races  in  the  Malay  Archi¬ 
pelago,  44. 

- ,  on  the  improvement  of  the 

eye,  173. 

- ,  on  the  walking-stick  insect, 

216. 

- ,  on  laws  of  geographical  dis¬ 
tribution,  380. 

- ,  on  the  Malay  Archipelago, 

415. 

- ,  on  mimetic  animals,  444. 

Walsh,  Mr.  B.  D.,  on  phytopha- 
gic  forms,  45. 

- ,  on  equal  variability,  149. 

Water,  fresh,  productions  of,  405. 

Water-hen,  169. 

Waterhouse,  Mr.,  on  Australian 
marsupials,  106. 

- ,  on  greatly  developed  parts 

being  variable,  141. 

- ,  on  the  cells  of  bees,  260. 

- ,  on  general  affinities,  446. 

Water-ouzel,  169. 

Watson,  Mr.  H.  C.,  on  range  of 
varieties  of  British  plants,  44, 
55. 

- ,  on  acclimatization,  134. 

- — ,  on  flora  of  Azores,  388. 


Watson,  Mr.  H.  C.,  on  rarity  of 
intermediate  varieties,  162 

- ,  on  Alpine  plants,  391. 

- ,  on  convergence,  120. 

- ,  on  the  indefinite  multipli 

cation  of  species,  121. 

Weale,  Mr.,  on  locusts  transport¬ 
ing  seeds,  387. 

Web  of  feet  in  water-birds,  170. 
Weismann,  Prof.,  on  the  causes 
of  variability,  7. 

- ,  on  rudimentary  organs,  471 

West  Indian  Islands,  mammals  of. 
415. 

Westwood,  on  species  in  large 
genera  being  closely  allied  to 
others,  54* 

- on  the  tarsi  of  Engidae,  147. 

- ,  on  the  antennae  of  hymenop- 

terous  insects,  432. 

Whales,  216. 

Wheat,  varieties  of,  103. 

White  Mountains,  flora  of,  390. 
Whittaker,  Mr.,  on  lined  of  es¬ 
carpment,  316. 

Wichura,  Max,  on  hybrids,  294, 
296,  307. 

Wings,  reduction  of  size,  130. 

- of  insects  homologous  with 

branchiae,  176. 

- ,  rudimentary,  in  insects, 

467. 

Wolf,  crossed  with  dog,  248. 

- of  Falkland  Isles,  414. 

Wollaston,  Mr.,  on  varieties  of 
insects,  45. 

- ,  on  fossil  varieties  of  shells 

in  Madeira,  49. 

Wollaston,  Mr.,  on  colors  of  in¬ 
sects  on  sea- shore,  127. 

- ,  on  wingless  beetles,  129. 

- ,  on  rarity  of  intermediate 

varieties,  162. 

- ,  on  insular  insects,  410. 

- ,  on  land-shells  of  Madeira 

naturalized,  42l. 

Wolves,  varieties  of,  83. 
Woodcock  with  earth  attached  to 
leg,  387. 

Woodpecker  habits  of,  108. 

- ,  green  color  of,  187. 


538 


INDEX. 


Woodward,  Mr.,  on  the  duration 
of  specific  forms,  326. 

- ,  on  Pyrgoma,  336. 

- ,  on  the  continuous  succession 

of  genera,  346. 

* - .  on  the  succession  of  types, 

367. 

VY  orld,  species  changing  simul¬ 
taneously  throughout,  352. 

Wright,  Mr.  Chauncey,  on  the 
giraffe,  211. 

- - ,  on  abrupt  modifications, 

240. 


Wrens,  nest  of,  276. 

Wyman,  Prof.,  on  correlation  of 
color  and  effects  of  poison,  11. 
- ,  on  the  cells  of  the  bee,  262. 

Youatt,  Mr.,  on  selection,  27. 

- ,  on  sub  breeds  of  sheep,  31. 

- ,  on  rudimentary  horns  in 

young  cattle,  472. 

Zanthoxylon,  206. 

Zebra,  stripes  on,  152. 

Zeuglodon,  357. 


TOE  END. 


POPULAR  LITERATURE  FOR  THE  MASSES, 

COMPRISING  CHOICE  SELECTIONS  FROM  THE 
TREASURES  OF  THE  WORLD’S  KNOWLEDGE, 
ISSUED  IN  A  SUBSTANTIAL  AND  ATTRACTIVE 
CLOTH  BINDING,  AT  A  POPULAR  PRICE 


BURT'S  HOME  LIBRARY  is  a  series  which 
Includes  the  standard  works  of  the  world's  test  literature, 
hound  in  uniform  cloth  binding,  gilt  tops,  embracing 
chiefly  selections  from  writers  of  the  most  notable 
English,  American  and  Foreign  Fiction,  together  with 
many  important  works  in  the  domains 
of  History,  Biography,  Philosophy, 

Travel,  Poetry  and  the  Essays. 

A  glance  at  the  following  annexed 
list  of  titles  and  authors  will  endorse 
the  claim  that  the  publishers  make 
for  it — that  it  is  the  most  compre¬ 
hensive,  choice,  interesting,  and  by 
far  the  most  carefully  selected  series 
of  standard  authors  for  world-wide 
reading  that  has  been  produced  by 
any  publishing  house  in  any  country,  and  that  at  prices 
so  cheap,  and  in  a  style  so  substantial  and  pleasing,  as  to 
win  for  it  millions  of  readers  and  the  approval  and 
commendation,  not  only  of  the  book  trade  throughout 
the  American  continent,  but  of  hundreds  of  thousands  of 
librarians,  clergymen,  educators  and  men  of  letters 
interested  in  the  dissemination  of  instructive,  entertaining 
and  thoroughly  wholesome  reading  matter  for  the  masses. 

,y 

rSEB  FOLLOWING  PAGBSl 


BURT’S  HOME  LIBRARY.  Cloth.  Gilt  Top*.  Price,  $1. (HI 


Abbe  Constantin.  By  Ludovic 

Halevy. 

Abbott,  By  Sir  Walter  Scott. 
Adam  Bede.  By  George  Eliot. 
Addison’s  Essays.  Edited  by  John 
Richard  Green. 

Aeneid  of  Virgil.  Translated  by 
John  Connington. 

Aesop’s  Fables. 

Alexander,  the  Great,  Life  of.  By 

John  Williams. 

Alfred,  the  Gr-eat,  Life  of.  By  Thomas 

Hughes. 

Alhambra.  By  Washington  Irving. 
Alice  in  Wonderland,  and  Through  the 
Looking-Glass.  By  Lewis  Carroll 
Alice  Lorraine.  By  R.  D.  Blackmore 
Al)  Sorts  and  Conditions  of  Men.  By 
Walter  Besant. 

Alton  Locke.  By  Charles  Kingsley. 
Amiel’s  JournaL  Translated  by 
Mrs.  Humphrey  Ward. 

Andersen’s  Fairy  Tales. 

Anne  of  Geirstein.  By  Sir  Walter 
Scott. 

Antiquary.  By  Sir  Walter  Scott. 
Arabian  Nights*  Entertainments. 
Ardath.  By  Marie  Corelli. 

Arnold,  Benedict,  Life  of.  By  George 
Canning  Hill. 

Arnold’s  Poems.  By  Matthew 
Arnold. 

Around  the  World  in  the  Yacht  Sun¬ 
beam.  By  Mrs.  Brassey. 

Arundel  Motto.  By  Mary  Cecil 
Hay. 

At  the  Back  of  the  North  Wind.  By 

George  Macdonald. 

Attic  Philosopher.  By  Emile  Sou- 
vestre. 

Auld  Licht  Idylls.  By  James  M. 
Barrie. 

Aunt  Diana.  By  Rosa  N.  Carey. 
Autobiography  of  Benjamin  Franklin. 
Autocrat  of  the  Breakfast  Table.  By 
O.  W.  Kclmes. 

Averil.  By  Rosa  N.  Carey. 

Bacon’s  Essays.  By  Francis  Bacon. 
Barbara  Heathcote’s  Trial.  By  Rosa 
N.  Carey. 

Barnaby  Rudge.  By  Charles  Dick¬ 
ens. 

Barrack  Room  Ballads.  By  Rudyard 
Kipling. 

Betrothed.  By  Sir  Walter  Scott. 
Beulah.  By  Augusta  J.  Evans. 
Black  Beauty,  By  Anna  Sewall. 
Black  Dwarf.  By  Sir  Walter 
Scott. 

Black  Rock.  By  Ralph  Connor. 
Black  Tulip.  By  Alexandre  Dumas. 
Bleak  House.  By  Charles  Dickens. 
Blithedale  Romance.  By  Nathaniel 
Hawthorn*. 

Bondman.  By  Hall  Caine. 

Book  of  Golden  Deeds.  By  Char¬ 
lotte  M.  Yonge. 

Boone,  Daniel,  Life  of.  By  Cecil  B. 
Hartley.  ' 


Bride  of  Lammermoor.  By  Sir 

Walter  Scott. 

Bride  of  the  Nile.  By  George  Ebers 
Browning’s  Poems.  By  Elizabeth 
Barrett  Browning. 

Browning’s  Poems.  (selections.' 

By  Robert  Browning. 

Bryant’s  Poems,  (early.)  By  Will 
iam  Cullen  Bryant. 

Burgomaster’s  Wife.  By  George 
Ebers. 

Burn’s  Poems.  By  Robert  Burns. 
By  Order  of  the  King.  By  Victor. 

Hugo. 

Byron’s  Poems.  By  Lord  Byron. 
Caesar,  Julius,  Life  of.  By  James 
Anthony  Froude. 

Carson,  Kit,  Life  of.  By  Charles 

Burdett. 

Cary’s  Poems.  By  Alice  and  ProxB* 
Cary. 

Cast  Up  by  the  Sea.  By  Sir  Samuel 
Baker. 

Charlemagne  (Charles  the  Great),  Life 
of.  By  Thomas  Hodgkin,  D.  C.  L. 
Charles  Auchester.  By  E.  Berger. 
Character.  By  Samuel  Smiles. 
Charles  O’Malley.  By  Charles 
Lever. 

Chesterfield’s  Letters.  By  Lord  Ches¬ 
terfield. 

Chevalier  de  Maison  Rouge.  By 

Alexandre  Dumas. 

Chicot  the  Jester.  By  Alexandre 

Dumas. 

Children  of  the  Abbey.  By  Regina 

Maria  Roche. 

Child’s  History  of  England.  By 

Charles.  Dickens. 

Christmas  Stories.  By  Charles 
Dickens. 

Cloister  and  the  Hearth.  By  Charles 

Reade. 

Coleridge’s  Poems.  By  Samuel  Tay¬ 
lor  Coleridge. 

Columbus,  Christopher,  Life  of.  By 

Washington  Irving. 

Companions  of  Jehu.  By  Alexandre 

Dumas. 

Complete  Angler.  By  Walton  and 

Cotton. 

Conduct  of  Life.  By  Ralph  Waldo 

Emerson. 

Confessions  of  an  Opium  Eater.  By 

Thomas  de  Quincey. 

Conquest  of  Granada.  By  Washing¬ 
ton  Irving. 

Conscript.  By  Erckmann-Chatriaw. 
Conspiracy  of  Pontiac.  By  Francis 
Parkman,  Jr. 

Conspirators.  By  Alexandra  Du^ 

MAS. 

Consuelo.  By  George  Sand. 

Cook’s  Voyages.  By  Captain  Jambs 

Cook. 

Corinne.  By  Madame  de  Stabl. 
Countess  de  Cbarney.  By  Alexandrh 

Dumas. 

e  ^duate&s  GiudA.  By  £.  Marutt, 


BURT’S  HOME  LIBRARY.  Cloth.  Gilt  Tops.  Price,  SI.OO 


Countess  of  Rudolstadt.  By  George 

Sand. 

Count  Robert  of  Paris.  By  Sir 
Walter  Scott. 

Country  Doctor.  By  Honore  de 
Balzac. 

Courtship  of  Miles  Standish.  By  H.  W. 
Longfellow. 

Cousin  Maude.  By  Mary  J.  Holmes. 
Cranford.  By  Mrs.  Gaskell. 
Crockett*  David*  Life  of.  An  Autobi¬ 
ography. 

Cromwell,  Oliver,  Life  of.  By  Edwin 
Paxton  Hood. 

Crown  of  Wild  Olive.  By  John 
Ruskin’ 

Crusades.  By  Geo.  W.  Cox,  M.  A. 
Daniel  Deronda.  By  George  Eliot. 
Darkness  and  Daylight.  By  Mary  J. 
Holmes. 

Data  of  Ethics.  By  Herbert  Spen¬ 
cer. 

Daughter  of  an  Empress,  The.  By 
Louisa  Muhlbach. 

David  Copperfield.  By  Charles 
Dickens. 

Days  of  Bruce.  By  Grace  Aguilar. 
Deemster,  The.  By  Hall  Caine. 
Deerslayer,  The.  By  James  Feni- 
more  Cooper. 

Descent  of  Man.  By  Charles  Dar¬ 
win. 

Discourses  of  Epictetus.  Translated 
by  George  Long. 

Divine  Comedy.  (Dante.)  Trans¬ 
lated  by  Rev.  H.  F.  Carey. 
Dombey  &  Son.  By  Charles  Dickens. 
Donal  Grant.  By  George  Macdon¬ 
ald. 

Donovan.  By  Edna  Lyall. 

Dora  Deane.  By  Mary  J.  Holmes. 
Dove  in  the  Eagle’s  Nest.  By  Char¬ 
lotte  M.  Yonge. 

Dream  Life.  By  Ik  Marvel. 

Dr.  Jekyll  and  Mr.  Hyde.  By  R.  L. 
Stevenson. 

Duty.  By  Samuel  Smiles. 

Early  Days  of  Christianity.  By  F.  W. 
Farrar. 

East  Lynne.  By  Mrs.  Henry  Wood. 
Edith  Lyle’s  Secret.  By  Mary  J. 

)  Holmes. 

Education.  By  Herbert  Spencer. 

-  Egoist.  By  George  Meredith. 
Egyptian  Princess.  By  George 
Ebbrs. 

Eight  Hundred  Leagues  on  the  Ama¬ 
zon.  By  Jules  Verne. 

Eliot’s  Poems.  By  George  Eliot. 
Elizabeth  and  her  German  Garden. 
Elizabeth  (Queen  of  England),  Life  of. 

By  Edward  Spencer  Beesly,  M.A. 
Elsie  Venner.  By  Oliver  Wendell 
Holmes. 

Emerson’s  Essays,  (complete.)  By 
Ralph  Waldo  Emerson. 

Emerson’s  Poems.  By  Ralph  Waldo 
Emerson. 

English  Orphans.  By  Mary  J. 
Holmes, 


English  Traits.  By  R.  W.  Emerson. 
Essays  in  Criticism.  (First  and 
Second  Series.)  By  Matthew 
Arnold. 

Essays  of  Elia.  By  Charles  Lamb. 
Esther.  By  Rosa  N.  Carey. 
Ethelyn’s  Mistake.  By  Mary  J„ 
Holmes. 

Evangeline,  (with  notes.)  By  H. 

W.  Longfellow. 

Evelina.  By  Frances  Burney. 

Fair  Maid  of  Perth.  By  Sir  Walter 
Scott. 

Fairy  Land  of  Science.  By  Arabella 
B.  Buckley. 

Faust.  (Goethe.)  Translated  bi 
Anna  Swanwick. 

Felix  Holt.  By  George  Eliot. 
Fifteen  Decisive  Battles  of  the  World. 
By  E.  S.  Creasy. 

File  No.  1 13.  By  Emile  Gaboriau. 
Firm  of  Girdlestone.  By  A.  Conan 
Doyle. 

First  Principles.  By  Herbert  Spencer. 
First  Violin.  By  Jessie  Fothergill. 
For  Lilias.  By  Rosa  N.  Carey. 
Fortunes  of  Nigel.  By  Sir  Walter 
Scott. 

Forty-Five  Guardsmen.  By  Alexan¬ 
dre  Dumas. 

Foul  Play.  By  Charles  Reads. 
Fragments  of  Science.  By  John 
Tyndall. 

Frederick,  the  Great,  Life  of.  By 

Francis  Kugi.er. 

Frederick  the  Great  and  His  Court.  By 
Louisa  Muhlbach. 

French  Revolution.  By  Thomas  Car¬ 
lyle. 

From  the  Earth  to  the  Moon.  By 

Jules  Verne. 

Garibaldi,  General,  Life  of.  By  Theo¬ 
dore  Dwight. 

Gil  Bias,  Adventures  of.  Br  A.  R.  Lb 

Sage. 

Gold  Bug  and  Other  Tales.  By 

Edgar  A.  Poe. 

Gold  Elsie.  By  E.  Marlitt. 

Golden  Treasury.  By  Franck  T. 
Palgrave. 

Goldsmith’s  Poems.  By  Oliver 

Goldsmith. 

Grandfather’s  Chair.  By  Nathaniel 

Hawthorne. 

Grant,  Ulysses  S.,  Life  of.  By  J  T 

Headley. 

Gray’s  Poems.  By  Thomas  Gray. 
Great  Expectations.  By  Charles 
Dickens. 

Greek  Heroes.  Fairy  Tales  for  Mv 
Children.  By  Charles  Kingsley. 
Green  Mountain  Boys,  The.  By  D.  P. 
Thompson. 

Grimm’s  Household  Tales.  By  the 
Brothers  Grimm. 

Grimm’s  Popular  Tales.  By  the 

Brothers  Grimm. 

Gulliver’s  Travels.  By  Dean  Swift. 
Guy  Mannering.  By  Sir  Walter 
Scott. 


BURT’S  HOME  LIBRARY.  Cloth.  Gilt  Tops.  Price,  $1.00 


Hale,  Nathan,  the  Martyr  Spy.  By 
Charlotte  Molyneux  Holloway. 
Handy  Andy.  By  Samuel  Lover. 
Hans  of  Iceland.  By  Victor  Hugo. 
Hannibal,  the  Carthaginian,  Life  of. 

By  Thomas  Arnold,  M.  A. 

Hardy  Norseman,  A.  By  Edna  Lyall. 
Harold.  By  Bulwer-Lytton. 

Harry  Lorrequer.  By  Charles  Lever. 
Heart  of  Midlothian.  By  Sir  Walter 
Scott. 

Heir  of  Redclyffe.  By  Charlette  M. 
Yonge. 

Hemans’  Poems.  By  Mrs.  Felicia 
Hemans. 

Henry  Esmond.  By  Wm.  J£.  "Thack¬ 
eray. 

Henry,  Patrick,  Life  of  By  William 
Wirt. 

Her  Dearest  Foe  By  Mrs.  Alexan¬ 
der. 

Hereward.  Xy  Charles  Kingsley. 
Heriot’s  Choice.  By  Rosa  N.  Carey. 
Heroe?  and  Hero-Worship.  By 
Tyomas  Carlyle. 

HiawatLa.  (with  notes.)  By  H.  W. 
Longfellow. 

Hidden  Hand,  The.  (complete.)  By 
Mrs.  E.  D.  E.  N.  Southworth. 
History  of  a  Crime.  By  Victor 
Hugo. 

History  of  Civilization  in  Europe.  By 
M.  Guizot. 

Holmes’  Poems.  (  early)  By  Oliver 
Wendell  Holmes. 

Holy  Roman  Empire.  By  James 
Bryce. 

Homestead  on  the  Hillside.  By  Mary 
J.  Holmes. 

Hood’s  Poems.  By  Thomas  Hood. 
House  of  the  Seven  Gables.  By 
Nathaniel  Hawthorne. 
Hunchback  of  Notre  Dame.  By 

Victor  Hugo. 

Hypatia.  By  Charles  Kingsley. 
Hyperion.  By  Henry  Wadsworth 
Longfellow. 

Iceland  Fisherman,  By  Pierre  Loti. 
Idle  Thoughts  of  an  Idle  Fellow-  By 
Jerome  K.  Jerome. 

Iliad,  Pope’s  Translation. 

Inez.  By  Augusta  J.  Evans. 
Ingelow’s  Poems.  By  Jean  Ingelow. 
Initials.  By  the  Baroness  Taut- 

PHOEUS. 

intellectual  Life.  By  Philip  G. 
Hamerton. 

fca  the  Counsellor’s  House.  By  E. 
Marlitt. 

In  the  Golden  Days.  By  Edna 

L<YALL. 

In  the  Heart  of  the  Storm.  By 

Maxwell  Gray. 

In  the  Schillingscourt.  By  E.  Mar¬ 
litt. 

Ishmael.  (complete.)  By  Mrs.  E. 
D.  E.  N.  Southworth. 

It  Is  Never  Too  Late  to  Mend.  By 
Charles  Reaps. 


Ivanhoe.  By  Sir  Walter'  Scott. 
ane  Eyre.  By  Charlotte  Bronte 
effersen,  Thomas,  Life  of.  Bv 
Samuel  M.  Schmuckeh.,  LL.D. 
Joan  of  Arc,  Life  of.  By  Jules 
Michelet. 

John  Halifax,  Gentleman.  By  Miss 

Mulock 

Jones,  Joh*i  Paul,  Life  of.  By  James 

Otis.. 

Joseph  Balsamo.  By  Alexandre 

Dumas. 

Josephine,  Empress  of  France,  Life  of. 
By  Frederick  A.  Ober. 

Keats’  Poems.  By  John  Keats. 
Kenilworth.  By  Sir  Walter  ScoTit, 
Kidnapped.  By  R.  L.  Stevenson. 
King  Arthur  and  His  Noble  Knights. 

By  Mary  Macleod. 

Knickerbocker’s  History  of  New  York,* 
By  Washington  Irving. 

Knight  Errant.  By  Edna  Lyall.  *  , 
Koran.  Translated  by  George 
Sale. 

Lady  of  the  Lake,  (with  notes.)  By 
Sir  Walter  Scott. 

Lady  with  the  Rubies.  By  E.  Mar- 
litt. 

Lafayette,  Marquis  de.  Life  of.  By 
P.  C.  Headley. 

Lalla  Rookh.  (with  notes.)  By 
Thomas  Moore. 

Lamplighter.  By  Maria  S.  Cum¬ 
mins. 

Last  Days  of  Pompeii.  By  Bulwer- 

Lytton. 

Last  of  the  Barons.  By  Bulwer- 

Lytton. 

Last  of  the  Mohicans.  By  James 
Fenimore  Cooper. 

Lay  of  the  Last  Minstrel,  (with 
notes.)  By  Sir  Walter  Scott. 
Lee,  General  Robert  E.,  Life  of.  By 
G.  Mercer  Adam. 

Lena  Rivers.  By  Mary  J,  Holmes. 
Life  of  Christ.  By  Frederick  W. 
Farrar. 

Life  of  Jesus.  By  Ernest  Renan. 
Light  of  Asia.  By  Sir  Edwin 
Arnold. 

Light  That  Failed.  By  Rudyard 

Kipling. 

Lincoln,  Abraham,  Life  of.  By 

Henry  Ketcham. 

Lincoln’s  Speeches.  Selected  and 
Edited  by  G.  Mercer  Adam. 
Literature  and  Dogma.  By  Matthew 

Arnold. 

Little  Dorrit.  By  Charles  Dickens. 
Little  Minister.  By  James  M.  Barrie. 
Livingstone,  David,  Life  of.  By 
Thomas  Hughes,  • 

Longfellow’s  Poems.  (Early.)  By 
Henry  W.  Longfellow. 

Lorna  Doone.  By  R.  D.  Blackmore. 
Louise  de  la  Valliere.  By  Alexandre 
Dumas, 

Love  Me  Little,  Love  Me  Long.  By 
K  Charles  Reads, 


BURT’S  HOME  LIBRARY.  Cloth.  Qilt  Tops.  Price,  $1.00 


Lowell’s  Poems,  (early.)  By  James 
Russell  Lowell. 

Lucile.  By  Owen  Meredith. 
Macaria.  By  Augusta  J.  Evans. 
Macaulay’s  Literary  Essays.  By  T.  B. 
Macaulay. 

Macaulay’s  Poems.  By  Thomas  Bab- 
ington  Macaulay. 

Madame  Therese.  By  Erckmann- 
Chatrian. 

Maggie  Miller.  By  Mary  J.  Holmes. 
Magic  Skin.  _  By  Honore  de  Balzac. 
Mahomet,  Life  of.  By  Washington 
Irving. 

Makers  of  Florence.  By  Mrs.  Oli- 
phant. 

Makers  of  Venice.  By  Mrs.  Oli- 

PHANT. 

Man  and  Wife.  By  Wilkie  Collins. 
Man  in  the  Iron  Mask.  By  Alexan¬ 
dre  Dumas. 

Marble  Faun.  By  Nathaniel  Haw¬ 
thorne. 

Marguerite  de  la  Valois.  By  Alex¬ 
andre  Dumas. 

Marian  Grey.  By  Mary  J.  Holmes. 
Marius,  The  Epicurian.  By  Walter 
Pater. 

Marmion.  (With  Notes.)  By  Sir 
Walter  Scott. 

Marquis  of  Lossie.  By  George 
Macdonald. 

Martin  Chuzzlewit  By  Charles 
Dickens. 

Mary,  Queen  of  Scots,  Life  of.  By 
P.  C.  Headley. 

Mary  St.  John.  By  Rosa  N.  Carey. 
Master  of  Ballantrae,  The.  By.  R.  L. 

Stevenson. 

Masterman  Ready.  By  Captain  Mar- 

RYATT. 

Meadow  Brook.  By  Mary  J.  Holmes. 
Meditations  of  Marcus  Aurelius. 

Translated  by  George  Long. 
Memoirs  of  a  Physician.  By  Alexan¬ 
dre  Dumas. 

Merle’s  Crusade.  By  Rosa  N.  Carey. 
Micah  Clarke.  By  A.  Conan  Dolye. 
Michael  Strogoff.  By  Jules  Verne. 
Middlemarch.  By  George  Eliot. 
Midshipman  Easy.  By  Captain  Mar- 
ryatt 

Mildred.  By  Mary  J.  Holmes. 
Millbank.  By  Mary  J.  Holmes. 

Mill  on  the  Floss.  By  George  Eliot. 
Milton’s  Poems.  By  John  Milton. 
Mine  Own  People.  ByRudyardKip- 

LING. 

Minister’s  Wooing,  The.  By  Harriet 
Beecher  Stowe. 

Monastery.  By  Sir  Walter  Scott. 
Moonstone.  By  Wilkie  Collins. 
Moore’s  Poems.  By  Thomas  Moore 
Mosses  from  an  Old  Manse.  By 
Nathaniel  Hawthorne. 

Murders  in  the  Rue  Morgue.  By 
Edgar  Allen  Poe. 

Mysterious  Island.  By  Jules  Verne. 
Napoleon  Bonaparte,  Life  By  P. 
C.  Headley.  -  - 


Napoleon  and  His  Marshals.  By  J. 

T.  Headley. 

Natural  Law  in  the  Spiritual  World. 

By  Henry  Drummond. 

Narrative  of  Arthur  Gordon  Pym.  Bt' 
Edgar  Allan  Poe. 

Nature,  Addresses  and  Lectures,  By 
R.  W.  Emerson. 

Nellie’s  Memories.  By  Rosa  N. 
Carey. 

Nelson,  Admiral  Horatio,  Life  of.  By 

Robert  Southey. 

Newcomes.  By  William  M.  Tiiack« 

ERAY. 

Nicholas  Nickleby.  By  Chas.  Dick* 

ens. 

Ninety-Three.  By  Victor  Hugo. 

Not  Like  Other  Girls.  By  Rosa  N. 

Carey. 

Odyssey.  Pope’s  Translation. 

Old  Curiosity  Shop.  By  Charles 
Dickens. 

Old  Mam’selle’s  Secret.  By  E.  Mar- 
litt. 

Old  Mortality.  By  Sir  Walter 

Scott. 

Old  Myddleton’s  Money.  By  Mary 

Cecil  Hay. 

Oliver  Twist.  By  Chas.  Dickens. 
Only  the  Governess.  By  Rosa  N. 
Carey. 

On  the  Heights.  By  Bbrthold 
Auerbach. 

Oregon  Trail.  By  Francis  Park- 

man. 

Origin  of  Species.  By  Charles 
Darwin. 

Other  Worlds  than  Ours.  By  Rich¬ 
ard  Proctor. 

Our  Bessie.  By  Rosa  N.  Carey. 

Our  Mutual  Friend.  By  Charles 

Dickens. 

Outre-Mer.  By  H.  W.  Longfellow. 
Owl’s  Nest.  By  E.  Marlitt. 

Page  of  the  Duke  of  Savoy.  By 
Alexandre  Dumas. 

Pair  of  Blue  Eyes.  By  Thomas 
Hardy. 

Pan  Michael.  By  Henryk  Sxbn- 

KIEWICZ. 

Past  and  Present  By  Thos.  Car¬ 
lyle. 

Pathfinder.  By  Jambs  Fbnimorb 

Cooper. 

Paul  and  Virginia.  By  B.  db  St. 

Pierre. 

Pendennis.  History  of.  By  Wm.  M. 
Thackeray. 

Penn,  William,  Life  of.  By  W.  Hbp- 
worth  Dixon. 

Pere  Goriot.  By  Honors  db  Balzac. 
Peter,  the  Great  Life  of.  By  John 
Barrow. 

Peveril  of  the  Peak.  By  Sir  Walter, 

Scott. 

Phantom  Rickshaw,  The.  By  Run- 

yard  Kipling. 

Philip  IL  of  Spain,  Life  of.  By  Matt 
tin  A.  S.  Hums. 

Hfceiek,  By  X.  B.  Saintwr. 


BURT’S  HOME  LIBRARY.  Cloth.  OIItTops.  Price,  $1. Oft 


Pickwick  Papers.  By  Charles  Dick- 

.  EN.S- 

Pilgrim’s  Progress.  Br  Johh  Bunyan. 
Pillar  of  Fire.  By  Rev.  J.  H.  Inora 
ham. 

-Pilot.  By  James  Fenimore  Cooper. 
pioneers.  By  James  Fenimore 
Cooper. 

Pirate.  By  Sir  Walter  Scott. 

Plain  Tales  from  the  Hills.  By  Rud- 

yard  Kipling. 

Plato's  Dialogues.  Translated  by  J. 
Wright,  M.  A. 

Pleasures  of  Life.  By  Sir  John 

Lubbock. 

Poe’s  Poems.  By  Edgar  A.  Poe. 
Pope’s  Poems.  By  Alexander  Pope. 
Prairie,  By  James  F.  Cooper. 

Pride  and  Prejudice.  By  Jane  Aus¬ 
ten. 

Prince  of  the  House  of  David.  By 
Rev.  J.  H.  Ingraham. 

Princess  of  the  Moor.  3y  E.  Marlitt 
Princess  of  Thule.  By  William 
Black. 

Procter’s  Poems.  By  Adelaide  Proc¬ 
tor. 

Professor  at  the  Breakfast  Table.  By 
Oliver  Wendell  Holmes. 
Professor.  By  Charlotte  Bronte. 
Prue  and  I.  By  George  William 
Curtis 

Put  Yourself  in  His  Place.  By  Chas. 
Reads. 

Putnam,  General  Israel,  Life  of  By 

George  Canning  Hill. 

Queen  Hortense.  By  Louisa  Muhl- 
bach. 

Queenie’s  Whim.  By  Rosa  N.  Carey. 
Queen’s  Necklace.  By  Alexandre 
Dumas. 

Quentin  Durward.  By  Sir  Walter 
Scott. 

Rasselas,  History  of.  By  Samuel 
Johnson. 

Redgauntlet.  By  Sir  Walter  Scott. 
Red  Rover.  By  James  Fenimore 
Cooper. 

Regent’s  Daughter.  By  Alexandre 
Dumas. 

Reign  of  Law.  By  Duke  of  Argyle. 
Representative  Men.  By  Ralph 
Waldo  Emerson. 

Republic  of  Plato.  Translated  by 
Davies  and  Vaughan. 

Return  of  the  Native.  By  Thomas 
Hardy. 

Reveries  of  a  Bachelor.  By  Ik  Mar¬ 
vel. 

iceynard  the  Fox.  Edited  by  Joseph 
Jacobs. 

Rienzi.  By  Bulwer-Lytton. 
Richelieu,  Cardinal,  Life  of.  By 
Richard  Lodge. 

Robinson  Crusoe.  By  Daniel  Defoe. 
Rob  Roy.  By  Sir  Walter  Scott. 
Romance  of  Natural  History.  By  P 

H.  Gosse. 

Romance  of  Two  Worlds.  By  Marie  i 
Corelh.  .  * 


Romola.  By  George  Eliot. 

Rory  O’More.  By  Samuel  Lover 
Rose  Mather.  By  Mary  J.  Holmes. 
Rossetti’s  Poems.  By  Gabriel  Dante 

Rossetti. 

Royal  Edinburgh.  By  Mrs.  Oli- 

PHANT. 

Rutledge.  By  Mirian  Coles  Harris. 
Saint  Michael.  By  E.  Werner. 
Samantha  at  Saratoga.  By  Josiah 
Aller’s  Wife.  (Marietta  Hol¬ 
ley.) 

Sartor  Resartus.  By  Thomas  Car¬ 
lyle. 

Scarlet  Letter.  By  Nathaniel  Haw. 

HORNE. 

Schonberg-Cotta  Family.  By  Mrs 

Andrew  Charles. 

Schopenhauer’s  Essays.  Translated 
by  T.  B.  Saunders. 

Scottish  Chiefs.  By  Jane  Porter. 
Scott’s  Poems.  By  Sir  Walter 
Scott. 

Search  for  Basil  Lyndhurst.  By 
Rosa  N.  Carey. 

Second  Wife.  By  E.  Marlitt. 
Seekers  After  God.  By  F.  W.  Farrar. 
Self-Help.  By  Samuel  Smiles. 
Self-Raised,  (complete.)  By  Mrs. 

E.  D.  E.  N.  Southworth. 

Seneca’s  Morals. 

Sense  and  Sensibility.  By  Jane 

Austen. 

Sentimental  Journey.  By  Lawrence 

Sterne. 

Sesame  and  Lilies.  By  John  Ruskin. 
Shakespeare’s  Heroines.  By  Anna 

Jameson. 

Shelley’s  Poems.  By  Percy  Bysshe 

Shelley. 

Shirley.  By  Charlotte  Bronte 

Sign  of  the  Four.  By  A.  Conan 

Doyle. 

Silas  Marner.  By  George  Eliot 
Silence  of  Dean  Maitland.  By  Max* 

#  well  Gray. 

Sir  Gibbie.  By  George  Macdonald 
Sketch  Book.  By  Washington  Irv 
ing. 

Smith,  Captain  John,  Life  of.  By  W 

Gilmore  Simms. 

Socrates,  Trial  and  Death  of.  Trans- 
lated  by  F.  J.  Church,  M.  A. 

Soldiers  Three.  By  Rudyard  Kip« 
ling. 

|pringhaven.  By  R.  D.  Blackmore. 
Spy.  By  James  Fenimore  Cooper. 
Stanley,  Henry  M.,  African  Explorer! 

Life  of.  By  A.  Montefiore. 

Story  of  an  African  Farm.  By  Olive 
Schreiner. 

Story  of  John  G.  Paton.  Told  for 
Young  Folks.  By  Rev.  Jas. 
Paton. 

St.  Ronan’s  Well.  By  Sir  Walter 

Scott. 

St«ovrih  ScarIet*  A* 


